locking, include/llist: Use linux/atomic.h instead of asm/cmpxchg.h

Including an asm/ header directly is best avoided, so use linux/atomic.h
instead of asm/cmpxchg.h in linux/llist.h.

Signed-off-by: Will Deacon <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

include/linux/llist.h

···
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
+#include <linux/atomic.h>
 #include <linux/kernel.h>
-#include <asm/cmpxchg.h>
 
 struct llist_head {
 	struct llist_node *first;