s390/qeth: allow hsuid configuration in DOWN state

The qeth IP address mapping logic has been reworked recently. It
causes now problems to specify qeth sysfs attribute "hsuid" in DOWN
state, which is allowed. Postpone registering or deregistering of
IP-addresses in this case.

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>