can: sja1000: fix bug using library functions for skb allocation

Commit 7b6856a "can: provide library functions for skb allocation"
did not properly remove two lines of the SJA1000 driver resulting in
a 'skb_over_panic' when calling skb_put, as reported by Kurt.

Signed-off-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/can/sja1000/sja1000.c

@@ -321,8 +321,6 @@ static void sja1000_rx(struct net_device *dev)
 	if (fi & FI_RTR)
 		id |= CAN_RTR_FLAG;
 
-	cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
-	memset(cf, 0, sizeof(struct can_frame));
 	cf->can_id = id;
 	cf->can_dlc = dlc;
 	for (i = 0; i < dlc; i++)