vdpa/mlx5: prepare memory regions

vdpa/mlx5: prepare memory regions

In order to map the guest physical addresses used by the virtio device
guest side to the host physical addresses used by the HW as the host
side, memory regions are created.

By this way, for example, the HW can translate the addresses of the
packets posted by the guest and to take the packets from the correct
place.

The design is to work with single MR which will be configured to the
virtio queues in the HW, hence a lot of direct MRs are grouped to single
indirect MR.

Create functions to prepare and release MRs with all the related
resources that are required for it.

Create a new file mlx5_vdpa_mem.c to manage all the MR related code
in the driver.

Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Maxime Coquelin <maxime.coquelin@redhat.com>