s390/qeth: rely on kernel for feature recovery

When recovering a device, qeth needs to re-run the IPA commands that
enable all previously active HW features.
Instead of duplicating qeth_set_features(), let netdev_update_features()
recover the missing HW features from dev->wanted_features.

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