vdpa/mlx5: Rename control VQ workqueue to vdpa wq

vdpa/mlx5: Rename control VQ workqueue to vdpa wq

[ Upstream commit 218bdd20e56cab41a68481bc10c551ae3e0a24fb ]

A subesequent patch will use the same workqueue for executing other
work not related to control VQ. Rename the workqueue and the work queue
entry used to convey information to the workqueue.

Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20210909123635.30884-3-elic@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>