[PATCH] alpha: atomic dependency fix

My alpha build is exploding because asm/atomic.h now needs smb_mb(), which is
over in the (not included) system.h.

I fear what will happen if I include system.h into atomic.h, so let's put the
barriers into their own header file.

Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-alpha/atomic.h

@@ -1,6 +1,8 @@
 #ifndef _ALPHA_ATOMIC_H
 #define _ALPHA_ATOMIC_H
 
+#include <asm/barrier.h>
+
 /*
  * Atomic operations that C can't guarantee us.  Useful for
  * resource counting etc...