idpf: add 4-byte completion descriptor definition

idpf: add 4-byte completion descriptor definition

In the queue-based scheduling mode, Tx completion descriptor is 4 bytes
comparing to 8 bytes in flow-based.
Add definition for it and allocate the corresponding amount of memory
for the descriptors during the completion queue creation.
This does not include handling 4-byte completions during Tx polling, as
for now, the only user of QB will be XDP, which has its own routines.

Signed-off-by: Michal Kubiak <michal.kubiak@intel.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Tested-by: Ramu R <ramu.r@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>