libceph: kill ceph_none_authorizer::reply_buf

We never receive authorizer replies with cephx disabled, so it is
bogus. Also, it still uses the old zero-length array style.

Reported-by: Gustavo A. R. Silva <[e-mail]>
Signed-off-by: Ilya Dryomov <[e-mail]>

net/ceph/auth_none.c

···
 	auth->authorizer = (struct ceph_authorizer *) au;
 	auth->authorizer_buf = au->buf;
 	auth->authorizer_buf_len = au->buf_len;
-	auth->authorizer_reply_buf = au->reply_buf;
-	auth->authorizer_reply_buf_len = sizeof (au->reply_buf);
+	auth->authorizer_reply_buf = NULL;
+	auth->authorizer_reply_buf_len = 0;
 
 	return 0;
 }

net/ceph/auth_none.h

···
 	struct ceph_authorizer base;
 	char buf[128];
 	int buf_len;
-	char reply_buf[0];
 };
 
 struct ceph_auth_none_info {