vDPA/ifcvf: decouple vq irq requester from the adapter

This commit decouples the vq irq requester from the adapter,
so that these functions can be invoked since probe.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Cc: stable@vger.kernel.org
Message-Id: <20221125145724.1129962-7-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>