parisc: Use double word condition in 64bit CAS operation

The attached change fixes the condition used in the "sub" instruction.
A double word comparison is needed.  This fixes the 64-bit LWS CAS
operation on 64-bit kernels.

I can now enable 64-bit atomic support in GCC.

Cc: <stable@vger.kernel.org>
Signed-off-by: John David Anglin <dave.anglin>
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/kernel/syscall.S

@@ -821,7 +821,7 @@ cas2_action:
 	/* 64bit CAS */
 #ifdef CONFIG_64BIT
 19:	ldd,ma	0(%sr3,%r26), %r29
-	sub,=	%r29, %r25, %r0
+	sub,*=	%r29, %r25, %r0
 	b,n	cas2_end
 20:	std,ma	%r24, 0(%sr3,%r26)
 	copy	%r0, %r28