qeth: recognize vlan devices in layer3 mode

The qeth layer3 driver is notified about IP address changes.
Changes concerning qeth driven network interfaces have to be
forwarded to the OSA-card. This includes IP addresses of VLAN
interfaces with a qeth device as base device. Function
qeth_l3_verify_vlan_dev() determines if the net_device of the
IP event belongs to a vlan device belonging to a qeth device
as real device. This function is broken starting with commit
7ff0bcf6 , which means IP
addresses of VLAN devices are no longer set at the base qeth
device. The patch repairs function qeth_l3_verify_vlan_dev().

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>