net/mlx5: refactor vectorized Rx

net/mlx5: refactor vectorized Rx

Move the main processing cycle into a separate function:
rxq_cq_process_v. Put the regular rxq_burst_v function
to a non-arch specific file. Having all SIMD instructions
in a single reusable block is a first preparatory step to
implement vectorized Rx burst for MPRQ feature.

Pass a pointer to the storage of mbufs directly to the
rxq_copy_mbuf_v instead of calculating the pointer inside
this function. This is needed for the future vectorized Rx
routing which is going to pass a different pointer here.

Calculate the number of packets to replenish inside the
mlx5_rx_replenish_bulk_mbuf. Containing this logic in one
place allows us to do the same for MPRQ case.

Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>