Add a very rudimentary active buffer management NIC support.
For now it's like a core NIC without SR-IOV support.  Next
commits will extend its functionality.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NDirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>