scripts/checkstack.pl: add support for nios2

Adjust checkstack.pl for the nios2 architecture.

Link: http://lkml.kernel.org/r/20170116113052.15034-1-tklauser@distanz.ch
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Cc: Ley Foon Tan <lftan@altera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: tklauser

scripts/checkstack.pl

@@ -78,6 +78,9 @@
 	} elsif ($arch eq 'mips') {
 		#88003254:       27bdffe0        addiu   sp,sp,-32
 		$re = qr/.*addiu.*sp,sp,-(([0-9]{2}|[3-9])[0-9]{2})/o;
+	} elsif ($arch eq 'nios2') {
+		#25a8:	defffb04 	addi	sp,sp,-20
+		$re = qr/.*addi.*sp,sp,-(([0-9]{2}|[3-9])[0-9]{2})/o;
 	} elsif ($arch eq 'parisc' || $arch eq 'parisc64') {
 		$re = qr/.*ldo ($x{1,8})\(sp\),sp/o;
 	} elsif ($arch eq 'ppc') {