s390/qeth: don't use restricted offloads for local traffic

Current OSA models don't support TSO for traffic to local next-hops, and
some old models didn't offer TX CSO for such packets either.

So as part of .ndo_features_check, check if a packet's next-hop resides
on the same OSA Adapter. Opt out from affected HW offloads accordingly.

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