ceph: check inode type for CEPH_CAP_FILE_{CACHE,RD,REXTEND,LAZYIO}

These bits will have new meaning for directory inodes.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>