x86 cmpxchg.h: fix wrong comment

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

arch/x86/include/asm/cmpxchg.h

@@ -35,7 +35,7 @@ extern void __add_wrong_size(void)
 
 /* 
  * An exchange-type operation, which takes a value and a pointer, and
- * returns a the old value.
+ * returns the old value.
  */
 #define __xchg_op(ptr, arg, op, lock)					\
 	({								\