sfc: create inner-csum queues on EF10 if supported

If the MC reports the VXLAN_NVGRE datapath capability, then these queues
 can be used for checksum offload of encapsulated packets.

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