can: restart device even if dev_alloc_skb() fails

If dev_alloc_skb() failed in can_restart(), the device was left behind
in the bus-off state. This patch restarts the device nevertheless.

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>