scripts/checkstack.pl: Add openrisc support

Openrisc stack pointer is managed by decrementing r1. Add regexes to
recognize this.
Signed-off-by: Stafford Horne <shorne@gmail.com>

scripts/checkstack.pl

@@ -78,6 +78,9 @@ my (@stack, $re, $dre, $x, $xs, $funcre);
 	} elsif ($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 'openrisc') {
+		# c000043c:       9c 21 fe f0     l.addi r1,r1,-272
+		$re = qr/.*l\.addi.*r1,r1,-(([0-9]{2}|[3-9])[0-9]{2})/o;
 	} elsif ($arch eq 'parisc' || $arch eq 'parisc64') {
 		$re = qr/.*ldo ($x{1,8})\(sp\),sp/o;
 	} elsif ($arch eq 'ppc') {