s390/qeth: fix race when initializing the IP address table

The ucast IP table is utilized by some of the L3-specific sysfs attributes
that qeth_l3_create_device_attributes() provides. So initialize the table
_before_ registering the attributes.

Fixes: ebccc739 ("s390/qeth: add missing hash table initializations")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>