ARC: entry: replace 8 byte OR with 4 byte BSET

FAKE_RET_FROM_EXCEPTION drops down to pure kernel mode. It currently has
an 8 byte instruction which can be replaced with 4 byte BSET

This is applicable to both ARCv2 and ARCv3 entr code.

ARCv2 current
------------
00000804 <EV_Trap>:
...
 874:   216a 1280               lr      r9,[status32]
 878:   2146 1809               bic     r9,r9,0x20
 87c:   2105 1f89 8000 0000     or      r9,r9,0x80000000
                  ^^^^^^^^^
 884:   2029 8240               kflag   r9

ARCv2 after
----------
000007e0 <EV_Trap>:
...
 850:   216a 1280               lr      r9,[status32]
 854:   2150 1149               bclr    r9,r9,0x5
 858:   214f 17c9               bset    r9,r9,0x1f
 85c:   2029 8240               kflag   r9

Signed-off-by: Vineet Gupta <[email protected]>

Author: vineetgarc

arch/arc/include/asm/entry-arcv2.h

@@ -274,8 +274,8 @@
 
 .macro FAKE_RET_FROM_EXCPN
 	lr      r9, [status32]
-	bic     r9, r9, STATUS_AE_MASK
-	or      r9, r9, STATUS_IE_MASK
+	bclr    r9, r9, STATUS_AE_BIT
+	bset    r9, r9, STATUS_IE_BIT
 	kflag   r9
 .endm