correct comments in arm atom.s

Reference: /n/atom/patch/applied/atomcassig
Date: Wed May 28 00:02:22 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/libc/arm/atom.s	Wed May 28 00:02:22 2014
+++ /sys/src/libc/arm/atom.s	Wed May 28 00:02:22 2014
@@ -4,7 +4,7 @@
 #define	STREX(v,a,r)	WORD	$(0xe<<28|0x01800f90 | (a)<<16 | (r)<<12 | (v)<<0)
 
 /*
- * int cas(ulong *p, ulong ov, ulong nv);
+ * int cas(int *p, int ov, int nv);
  */
 
 TEXT	cas+0(SB),0,$0		/* r0 holds p */