fuse: annotate lock in fuse_reverse_inval_entry()

commit bda9a719 upstream.

Add missing inode lock annotatation; found by syzbot.

Reported-and-tested-by:  <syzbot+9f747458f5990eaa8d43@syzkaller.appspotmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>