net/i40e: announce request queue capability in PF

net/i40e: announce request queue capability in PF

A new feature requesting additional queues from PF is added in iavf;
before sending VIRTCHNL_OP_REQUEST_QUEUES op code, the offload
capability flag VIRTCHNL_VF_OFFLOAD_REQ_QUEUES will be checked.

And due to DPDK PF is still used by some cases, add this offload
capability flag in i40e PF.

Fixes: cbdbd360f77f ("net/i40e: support AVF basic interface")
Cc: stable@dpdk.org
Signed-off-by: Robin Zhang <robinx.zhang@intel.com>
Acked-by: Jeff Guo <jia.guo@intel.com>