vdpa/mlx5: prepare virtio queues

vdpa/mlx5: prepare virtio queues

The HW virtq object represents an emulated context for a VIRTIO_NET
virtqueue which was created and managed by a VIRTIO_NET driver as
defined in VIRTIO Specification.

Add support to prepare and release all the basic HW resources needed
the user virtqs emulation according to the rte_vhost configurations.

This patch prepares the basic configurations needed by DevX commands to
create a virtq.

Add new file mlx5_vdpa_virtq.c to manage virtq operations.

Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>