s390/qeth: don't erase configuration while probing

The HW trap and VNICC configuration is exposed via sysfs, and may have
already been modified when qeth_l?_probe_device() attempts to initialize
them. So (1) initialize the VNICC values a little earlier, and (2) don't
bother about the HW trap mode, it was already initialized before.

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