[RFC v1] net/mlx5: support new completion field for Multi-Packet RQ

Multi-Packet Receive Queue is to receive multiple packets on a single large
buffer. As it is supposed to have Rx CQEs in order from HW,
'consumed_stride' in CQE is accumulated to keep track of the current stride
index. However, it is safer to directly use 'stride_idx' in CQE to avoid
out-of-order situation which can possibly be caused by introducing new
features in the future.

If Rx CQE compression is enabled, HW can be configured to store the
'stride_idx' in a mini-CQE but this will need newer version of
library/driver along with firmware changes.

Signed-off-by: Yongseok Koh <redacted>