s390/qeth: vnicc Fix EOPNOTSUPP precedence

When getting or setting VNICC parameters, the error code EOPNOTSUPP
should have precedence over EBUSY.

EBUSY is used because vnicc feature and bridgeport feature are mutually
exclusive, which is a temporary condition.
Whereas EOPNOTSUPP indicates that the HW does not support all or parts of
the vnicc feature.
This issue causes the vnicc sysfs params to show 'blocked by bridgeport'
for HW that does not support VNICC at all.

Fixes: caa1f0b1

 ("s390/qeth: add VNICC enable/disable support")
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>