vdpa: do not block migration if device has cvq and x-svq=on

vdpa: do not block migration if device has cvq and x-svq=on

It was a mistake to forbid in all cases, as SVQ is already able to send
all the CVQ messages before start forwarding data vqs.  It actually
caused a regression, making impossible to migrate device previously
migratable.

Fixes: 36e4647247f2 ("vdpa: add vhost_vdpa_net_valid_svq_features")
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20230602143854.1879091-2-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>