[PATCH] ppc64: use smp_mb and smp_wmb

Use smp_mb and smp_wmb. In particular smp_wmb is lighter weight than wmb.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>