virtio-net: Fix vhost virtqueue notifiers for RSS

virtio-net: Fix vhost virtqueue notifiers for RSS

virtio_net_guest_notifier_pending() and virtio_net_guest_notifier_mask()
checked VIRTIO_NET_F_MQ to know there are multiple queues, but
VIRTIO_NET_F_RSS also enables multiple queues. Refer to n->multiqueue,
which is set to true either of VIRTIO_NET_F_MQ or VIRTIO_NET_F_RSS is
enabled.

Fixes: 68b0a6395f36 ("virtio-net: align ctrl_vq index for non-mq guest for vhost_vdpa")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit 1c188fc8cbffc5f05cc616cab4e1372fb6e6f11f)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>