vdpa: Restore hash calculation state

This patch introduces vhost_vdpa_net_load_rss() to restore
the hash calculation state at device's startup.

Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
Message-Id: <dbf699acff8c226596136a55a6abe35ebfeac8b0.1698194366.git.yin31149@gmail.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>