drivers: nxp_enet: Add get_config to re-enable ipv6 checksum acceleration

[decsny]

Previously, ipv6 being disabled was a dependency of the hw acceleration of the checksums for the nxp enet driver, because this ethernet has an errata causing icmpv6 checksum to not be supported (see #73518). Now, there is a new config type in ethernet api added in #73985 for checksum types, so we can re-enable hardware acceleration for ipv6 by implementing this type in the get_config api in this driver.

[pdgendt]

Nit: alignment

[hakehuang]

@decsny , with this PR.
in frdm_k64f, ipv6 does not work, and network only work when I hot plug the ethernet cable([00:00:15.021,000] net_icmpv6: ICMPv6 handling failure (-5)).

uart:~$
[00:00:03.713,000] <inf> phy_mc_ksz8081: PHY 0 is up
[00:00:03.713,000] <inf> phy_mc_ksz8081: PHY (0) Link speed 100 Mb, full duplex

*** Booting Zephyr OS build v4.0.0-rc3-1-gc879bbe27396 ***
[00:00:03.715,000] <inf> net_config: Initializing network
[00:00:03.715,000] <inf> net_config: Waiting interface 1 (0x20000df0) to be up...
[00:00:12.216,000] <inf> eth_nxp_enet_mac: Link is down
[00:00:15.019,000] <inf> eth_nxp_enet_mac: Link is up
[00:00:15.019,000] <inf> phy_mc_ksz8081: PHY 0 is up
[00:00:15.019,000] <inf> phy_mc_ksz8081: PHY (0) Link speed 100 Mb, full duplex

[00:00:15.020,000] <inf> net_config: Interface 1 (0x20000df0) coming up
[00:00:15.020,000] <inf> net_config: IPv4 address: 192.0.2.1
[00:00:15.021,000] <err> net_icmpv6: ICMPv6 handling failure (-5)
[00:00:15.122,000] <inf> net_config: IPv6 address: fd9a:9616:b8e9:0:4:9fff:fe96:eb61
uart:~$
[00:00:02.910,000] <inf> phy_mc_ksz8081: PHY 0 is up
[00:00:02.910,000] <inf> phy_mc_ksz8081: PHY (0) Link speed 100 Mb, full duplex

*** Booting Zephyr OS build v4.0.0-rc3-1-gc879bbe27396 ***
[00:00:02.912,000] <inf> net_config: Initializing network
[00:00:02.912,000] <inf> net_config: Waiting interface 1 (0x20000df0) to be up...
uart:~$

[decsny]

@hakehuang k64f is the platform I tested on, and I used the echo server example you put originally on your issue #73518, which now works, are you saying, it doesn't work if the cable is connected before boot?

[hakehuang]

it doesn't work if the cable is connected before boot?
@decsny
this is a common problem I find this in main branch as well. but the ICMPv6 handling failure (-5)) is found on this PR.
I report one issue #81274 which is introduced by 6984fd8

[hakehuang]

regression test pass