can: slcan: slc_xmit(): use can_dropped_invalid_skb() instead of manual check

slcan does a manual check in slc_xmit() to verify if the skb is valid.
This check is incomplete, use instead can_dropped_invalid_skb().

Link: https://lore.kernel.org/all/20220514141650.1109542-2-mailhol.vincent@wanadoo.frSigned-off-by: NVincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/slcan.c

@@ -359,8 +359,8 @@ static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct slcan *sl = netdev_priv(dev);
 
-	if (skb->len != CAN_MTU)
-		goto out;
+	if (can_dropped_invalid_skb(dev, skb))
+		return NETDEV_TX_OK;
 
 	spin_lock(&sl->lock);
 	if (!netif_running(dev))  {