slcan: ldisc generated skbs are received in softirq context

As this discussion pointed out

http://marc.info/?l=linux-netdev&m=131257225602375

netdevices that are based on serial line disciplines should use netif_rx_ni()
when pushing received socketbuffers into the netdev rx queue.

Following commit 61485160 ("slip: fix NOHZ
local_softirq_pending 08 warning") this patch updates the slcan driver
accordingly.
Signed-off-by: NOliver Hartkopp <socketcan@hartkopp.net>
CC: Matvejchikov Ilya <matvejchikov@gmail.com>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/can/slcan.c

@@ -197,7 +197,7 @@ static void slc_bump(struct slcan *sl)
 	skb->ip_summed = CHECKSUM_UNNECESSARY;
 	memcpy(skb_put(skb, sizeof(struct can_frame)),
 	       &cf, sizeof(struct can_frame));
-	netif_rx(skb);
+	netif_rx_ni(skb);
 
 	sl->dev->stats.rx_packets++;
 	sl->dev->stats.rx_bytes += cf.can_dlc;