virtio_pci: use helper function is_power_of_2()

Use helper function is_power_of_2() to check if num is power of two.
Minor readability improvement.

Signed-off-by: Shaoqin Huang <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Reviewed-by: Xuan Zhuo <[e-mail]>

drivers/virtio/virtio_pci_modern.c

···
 	if (!num || vp_modern_get_queue_enable(mdev, index))
 		return ERR_PTR(-ENOENT);
 
-	if (num & (num - 1)) {
+	if (!is_power_of_2(num)) {
 		dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num);
 		return ERR_PTR(-EINVAL);
 	}