pds_vdpa: clean and reset vqs entries

Make sure that we initialize the vqs[] entries the same
way both for initial setup and after a vq reset.

Fixes: 151cc834 ("pds_vdpa: add support for vdpa and vdpamgmt interfaces")
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Message-Id: <20230711042437.69381-4-shannon.nelson@amd.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>