ceph: move spinlocking into ceph_encode_locks_to_buffer and ceph_count_locks

There is only a single call site for each of these functions, and the
caller takes the i_lock prior to calling them and drops it just
afterward. Move the spinlocking into the functions instead.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Acked-by: Christoph Hellwig <hch@lst.de>