qeth: enable interface setup if LAN is offline

Device initialization of a qeth device contains a STARTLAN step.
This step may fail, if cable is not yet plugged in. The qeth device
stays in state HARDSETUP until cable is plugged in. This prevents
further preparational initialization steps of the qeth device and
its network interface. This patch makes sure initialization of qeth
device continues, even though cable is not yet plugged in.
Once carrier is available, qeth is notified, triggers a recovery
which results in a working network interface.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>