[PATCH] hugetlbfs: add lock annotation to hugetlbfs_forget_inode()

hugetlbfs_forget_inode releases inode_lock.  Add a lock annotation to this
function so that sparse can check callers for lock pairing, and so that
sparse will not complain about this functions since it intentionally uses
the lock in this manner.

Signed-off-by: Josh Triplett <josh@freedesktop.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>