ARC: entry: replace 8 byte ADD.ne with 4 byte ADD2.ne

ARCv2 current
------------
000007e0 <EV_Trap>:
 7e0:   2482 3c01               sub     sp,sp,112
 7e4:   1c28 3006               std     r0r1,[sp,40]
 7e8:   1c30 3086               std     r2r3,[sp,48]
 7ec:   1c38 3106               std     r4r5,[sp,56]
 7f0:   1c40 3186               std     r6r7,[sp,64]
 7f4:   1c48 3206               std     r8r9,[sp,72]
 7f8:   1c50 3286               std     r10r11,[sp,80]
 7fc:   1c58 37c0               st      blink,[sp,88]
 800:   1c0c 36c0               st      fp,[sp,12]
 804:   1c18 3680               st      gp,[sp,24]
 808:   1c10 3780               st      r30,[sp,16]
 80c:   1c14 3300               st      r12,[sp,20]
 810:   226a 1340               lr      r10,[aux_user_sp]
 814:   22ca 1702               mov.ne  r10,sp
 818:   22c0 1f82 0000 0070     add.ne  r10,r10,0x70
                  ^^^^^^^^^
With fix
--------
000007b4 <EV_Trap>:
 7b4:   2482 3c01               sub     sp,sp,112
 7b8:   1c28 3006               std     r0r1,[sp,40]
 7bc:   1c30 3086               std     r2r3,[sp,48]
 7c0:   1c38 3106               std     r4r5,[sp,56]
 7c4:   1c40 3186               std     r6r7,[sp,64]
 7c8:   1c48 3206               std     r8r9,[sp,72]
 7cc:   1c50 3286               std     r10r11,[sp,80]
 7d0:   1c58 37c0               st      blink,[sp,88]
 7d4:   1c0c 36c0               st      fp,[sp,12]
 7d8:   1c18 3680               st      gp,[sp,24]
 7dc:   1c10 3780               st      r30,[sp,16]
 7e0:   1c14 3300               st      r12,[sp,20]
 7e4:   226a 1340               lr      r10,[aux_user_sp]
 7e8:   22ca 1702               mov.ne  r10,sp
 7ec:   22d5 1722               add2.ne r10,r10,0x1c
Signed-off-by: Vineet Gupta <vgupta@kernel.org>

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

@@ -167,7 +167,7 @@
 
 	; ISA requires ADD.nz to have same dest and src reg operands
 	mov.nz	r10, sp
-	add.nz	r10, r10, SZ_PT_REGS	; K mode SP
+	add2.nz	r10, r10, SZ_PT_REGS/4	; K mode SP
 
 	st	r10, [sp, PT_sp]	; SP (pt_regs->sp)