sfc: interrogate MAE capabilities at probe time

Different versions of EF100 firmware and FPGA bitstreams support different
 matching capabilities in the Match-Action Engine.  Probe for these at
 start of day; subsequent patches will validate TC offload requests
 against the reported capabilities.

Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>