[NETROM/AX.25/ROSE]: Remove useless tests

Remove error tests that have already been performed by the caller.

Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ax25/af_ax25.c

@@ -1700,11 +1700,7 @@ static int ax25_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 	}
 
 	case SIOCGSTAMP:
-		if (sk != NULL) {
-			res = sock_get_timestamp(sk, argp);
-			break;
-	 	}
-		res = -EINVAL;
+		res = sock_get_timestamp(sk, argp);
 		break;
 
 	case SIOCAX25ADDUID:	/* Add a uid to the uid/call map table */