s390/qeth: don't worry about IPs on VLAN removal

When removing a VLAN ID on a L3 device, the driver currently attempts to
walk and unregister the VLAN device's IP addresses.
This can be safely removed - before qeth_l3_vlan_rx_kill_vid() even gets
called, we receive an inet[6]addr event for each IP on the device and
qeth_l3_handle_ip_event() unregisters the address accordingly.

Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>