vDPA/ifcvf: a vendor driver should not set _CONFIG_S_FAILED

VIRTIO_CONFIG_S_FAILED indicates the guest driver has given up
the device due to fatal errors. So it is the guest decision,
the vendor driver should not set this status to the device.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20230526145254.39537-6-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>