ceph: handle fscrypt fields in cap messages from MDS

Handle the new fscrypt_file and fscrypt_auth fields in cap messages. Use
them to populate new fields in cap_extra_info and update the inode with
those values.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-and-tested-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>