vdpa/mlx5: Allow modifying multiple vq fields in one modify command

Add a bitmask variable that tracks hw vq field changes that
are supposed to be modified on next hw vq change command.

This will be useful to set multiple vq fields when resuming the vq.

Reviewed-by: Gal Pressman <gal@nvidia.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Message-Id: <20231225151203.152687-3-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>