virtio-console: Use virtio_config_val() for retrieving config

This patch modifies virtio-console to use virtio_config_val() instead
of a 'if(virtio_has_feature()) vdev->config->get()' construct to retrieve
optional values from the config space.

Cc: Amit Shah <amit.shah@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/char/virtio_console.c

@@ -1675,13 +1675,11 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
 
 	multiport = false;
 	portdev->config.max_nr_ports = 1;
-	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT)) {
-		multiport = true;
-		vdev->config->get(vdev, offsetof(struct virtio_console_config,
+	if (virtio_config_val(vdev, VIRTIO_CONSOLE_F_MULTIPORT,
+			      offsetof(struct virtio_console_config,
 				       max_nr_ports),
-				  &portdev->config.max_nr_ports,
-				  sizeof(portdev->config.max_nr_ports));
-	}
+			      &portdev->config.max_nr_ports) == 0)
+		multiport = true;
 
 	err = init_vqs(portdev);
 	if (err < 0) {