Add native netmap support to ixl.
Preliminary tests indicate 32 Mpps on tx, 24 Mpps on rx
with source and receiver on two different ports of the same 40G card.
Optimizations are likely possible.
The code follows closely the one for ixgbe so i do not
expect stability issues.

Hardware kindly supplied by Intel.

Reviewed by: Jack Vogel
MFC after: 1 week