[PATCH] msi: use kmem_cache_zalloc()

Simpler, cleaner.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>