[PATCH] mbcache: add lock annotation for __mb_cache_entry_release_unlock()

__mb_cache_entry_release_unlock releases mb_cache_spinlock, so annotate it
accordingly.

Signed-off-by: Josh Triplett <josh@freedesktop.org>
Cc: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>