net/mlx5: support shared Rx queue port data path

net/mlx5: support shared Rx queue port data path

When receive packet, mlx5 PMD saves mbuf port number from
RxQ data.

To support shared RxQ, save port number into RQ context as user index.
Received packet resolve port number from CQE user index which derived
from RQ context.

Legacy Verbs API doesn't support RQ user index setting, still read from
RxQ port number.

Signed-off-by: Xueming Li <xuemingl@nvidia.com>
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>