common/iavf: add enumeration for Rx descriptor ID

common/iavf: add enumeration for Rx descriptor ID

Support for allowing VFs to negotiate the descriptor format was added
previously.

This support requires that the VF specify which descriptor format to use
when requesting Rx queues. The VF is supposed to request the set of
supported formats via the new VIRTCHNL_OP_GET_SUPPORTED_RXDIDS, and then
set one of the supported formats in the rxdid field of the
virtchnl_rxq_info structure.

The virtchnl.h header does not provide an enumeration of the format
values. The existing implementations in the PF directly use the values
from the DDP package.

Make the formats explicit by defining an enumeration of the RXDIDs.
Provide an enumeration for the values as well as the bit positions as
returned by the supported_rxdids data from the
VIRTCHNL_OP_GET_SUPPORTED_RXDIDS.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Beilei Xing <beilei.xing@intel.com>