[Bluetooth] Remove MTU check for the L2CAP raw socket

The L2CAP raw socket is associated with the signal channel and the
check for the maximum transfer unit makes no sense here.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/l2cap.c

@@ -770,7 +770,7 @@ static int l2cap_sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct ms
 		return -EOPNOTSUPP;
 
 	/* Check outgoing MTU */
-	if (len > l2cap_pi(sk)->omtu)
+	if (sk->sk_type != SOCK_RAW && len > l2cap_pi(sk)->omtu)
 		return -EINVAL;
 
 	lock_sock(sk);