vdpa: stop all svq on device deletion

vdpa: stop all svq on device deletion

Not stopping them leave the device in a bad state when virtio-net
fronted device is unplugged with device_del monitor command.

This is not triggable in regular poweroff or qemu forces shutdown
because cleanup is called right after vhost_vdpa_dev_start(false).  But
devices hot unplug does not call vdpa device cleanups.  This lead to all
the vhost_vdpa devices without stop the SVQ but the last.

Fix it and clean the code, making it symmetric with
vhost_vdpa_svqs_start.

Fixes: dff4426fa656 ("vhost: Add Shadow VirtQueue kick forwarding capabilities")
Reported-by: Lei Yang <leiyang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20230209170004.899472-1-eperezma@redhat.com>
Tested-by: Laurent Vivier <lvivier@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>