libceph: kill bad_proto ceph connection op

No code sets a bad_proto method in its ceph connection operations
vector, so just get rid of it.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>

include/linux/ceph/messenger.h

@@ -31,9 +31,6 @@ struct ceph_connection_operations {
 	int (*verify_authorizer_reply) (struct ceph_connection *con, int len);
 	int (*invalidate_authorizer)(struct ceph_connection *con);
 
-	/* protocol version mismatch */
-	void (*bad_proto) (struct ceph_connection *con);
-
 	/* there was some error on the socket (disconnect, whatever) */
 	void (*fault) (struct ceph_connection *con);