vDPA/ifcvf: virt queue ops take immediate actions

In this commit, virtqueue operations including:
set_vq_num(), set_vq_address(), set_vq_ready()
and get_vq_ready() access PCI registers directly
to take immediate actions.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20230526145254.39537-2-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>