ifcvf: ignore continuous setting same status value

User space may try to set status of same value multiple times,
this patch handles this case more efficiently by ignoring the
setting of the same status value.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Link: https://lore.kernel.org/r/1591352835-22441-3-git-send-email-lingshan.zhu@intel.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/ifcvf/ifcvf_main.c

@@ -179,6 +179,9 @@ static void ifcvf_vdpa_set_status(struct vdpa_device *vdpa_dev, u8 status)
 	adapter = dev_get_drvdata(vdpa_dev->dev.parent);
 	status_old = ifcvf_get_status(vf);
 
+	if (status_old == status)
+		return;
+
 	if ((status_old & VIRTIO_CONFIG_S_DRIVER_OK) &&
 	    !(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
 		ifcvf_stop_datapath(adapter);