net: tc-mapping: Fix SKIP_FOR_HIGH_PRIO

[ClaCodes]

Based on #93341

Adjust the way the SKIP option worked. Before this patch, a constant
priority offset was considered "high priority" this had the effect, that
the threads assigned to work on the priority were effectively usesless.
To fix it, consider this immediate handling as a pseudo-queue and compute
the tc-thead-mapping based on the effective count (+1 if skipping is
enabled). This makes it so that all threads are usefull and the
high-priority skip-path is considered as a pseudo tc-thread.

Running net filter on this sample (adjusted to 7 queues with skip enabled) after:

uart:~$ net filter                                                                                                                                                                                                                                 
Rule  Type        Verdict   Pkt-Prio  Queue  Thread-Prio  Tests                                                                                                                                                                                    
[ 1]  recv        CONTINUE         1      0           15  1    eth type[0x007b]                                                                                                                                                                    
[ 2]  recv        CONTINUE         0      1           13  1    eth type[0x007c]                                                                                                                                                                    
[ 3]  recv        CONTINUE         2      2           11  1    eth type[0x007d]                                                                                                                                                                    
[ 4]  recv        CONTINUE         3      3            9  1    eth type[0x007e]                                                                                                                                                                    
[ 5]  recv        CONTINUE         4      4            7  1    eth type[0x007f]                                                                                                                                                                    
[ 6]  recv        CONTINUE         5      5            5  1    eth type[0x0080]                                                                                                                                                                    
[ 7]  recv        CONTINUE         6      6            3  1    eth type[0x0081]                                                                                                                                                                    
[ 8]  recv        CONTINUE         7      7         SKIP  1    eth type[0x0082]                                                                                                                                                                    
[ 9]  recv        OK             N/A    N/A          N/A  0    

vs before

uart:~$ net filter
Rule  Type        Verdict   Pkt-Prio  Queue  Thread-Prio  Tests
[ 1]  recv        CONTINUE         1      0           15  1    eth type[0x007b]
[ 2]  recv        CONTINUE         0      1           13  1    eth type[0x007c]
[ 3]  recv        CONTINUE         2      2           11  1    eth type[0x007d]
[ 4]  recv        CONTINUE         3      3         SKIP  1    eth type[0x007e]
[ 5]  recv        CONTINUE         4      4         SKIP  1    eth type[0x007f]
[ 6]  recv        CONTINUE         5      4         SKIP  1    eth type[0x0080]
[ 7]  recv        CONTINUE         6      5         SKIP  1    eth type[0x0081]
[ 8]  recv        CONTINUE         7      6         SKIP  1    eth type[0x0082]
[ 9]  recv        OK             N/A    N/A          N/A  0    
uart:~$ 

Without this patch, several tc-queue-threads are present but idling.

For applications with the following config, it would have no effect:

CONFIG_NET_TC_MAPPING_STRICT=y
CONFIG_NET_TC_RX_COUNT=1
CONFIG_NET_TC_RX_SKIP_FOR_HIGH_PRIO=y

due to

#define PRIORITY2TC_2 {0, 0, 0, 0, 1, 1, 1, 1}

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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