vdpa: Add vhost_vdpa_net_load_offloads()

vdpa: Add vhost_vdpa_net_load_offloads()

This patch introduces vhost_vdpa_net_load_offloads() to
restore offloads state at device's startup.

Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
Message-Id: <7e2b5cad9c48c917df53d80dec27dbfeb513e1a3.1685704856.git.yin31149@gmail.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Tested-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>