can: switch carrier on if device was stopped while in bus-off state

This patch fixes a problem when a device is stopped while in the
bus-off state. Then the carrier remains off forever.

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