qeth: NAPI support for l2 and l3 discipline

This patch adds NAPI support to the qeth layer 2 and layer 3
discipline. It is important to understand that we can not enable/disable
IRQs as usual, we have to use the corresponding new QDIO interface.
Also to not overdraw the budget we have to stop and restart buffer
processing at any point during processing a bulk of QDIO buffers.
Having the driver NAPI enabled it is possible to turn on GRO for the
layer 3 discipline.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>