qeth: postpone freeing of qdio memory

To guarantee that a qdio ccw_device no longer touches the
qdio memory shared with Linux, the qdio ccw_device should
be offline when freeing the qdio memory. Thus this patch
postpones freeing of qdio memory.

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