vDPA: fix spars cast warning in vdpa_dev_net_mq_config_fill

This commit fixes spars warnings: cast to restricted __le16
in function vdpa_dev_net_mq_config_fill()

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220929014555.112323-6-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>