media: sunxi: sun6i_mipi_csi2.c/sun8i_a83t_mipi_csi2.c: clarify error handling

Both sun6i_mipi_csi2.c and sun8i_a83t_mipi_csi2.c have the same issue:
the comment before the ret = 0 assignment is incorrect, drop it and
always assign the result of the v4l2_subdev_call(..., 0) to ret.

In the disable label check for !on and set ret to 0 in that case.

This fixes two smatch warnings:

drivers/media/platform/sunxi/sun6i-mipi-csi2/sun6i_mipi_csi2.c:193 sun6i_mipi_csi2_s_stream() warn: missing error code 'ret'
drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/sun8i_a83t_mipi_csi2.c:225 sun8i_a83t_mipi_csi2_s_stream() warn: missing error code 'ret'

Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/platform/sunxi/sun6i-mipi-csi2/sun6i_mipi_csi2.c

···
 	unsigned int lanes_count =
 		csi2_dev->bridge.endpoint.bus.mipi_csi2.num_data_lanes;
 	unsigned long pixel_rate;
-	/* Initialize to 0 to use both in disable label (ret != 0) and off. */
-	int ret = 0;
+	int ret;
 
 	if (!source_subdev)
 		return -ENODEV;
 
 	if (!on) {
-		v4l2_subdev_call(source_subdev, video, s_stream, 0);
+		ret = v4l2_subdev_call(source_subdev, video, s_stream, 0);
 		goto disable;
 	}
 
···
 	return 0;
 
 disable:
+	if (!on)
+		ret = 0;
 	phy_power_off(dphy);
 	sun6i_mipi_csi2_disable(csi2_dev);
 

drivers/media/platform/sunxi/sun8i-a83t-mipi-csi2/sun8i_a83t_mipi_csi2.c

···
 	unsigned int lanes_count =
 		csi2_dev->bridge.endpoint.bus.mipi_csi2.num_data_lanes;
 	unsigned long pixel_rate;
-	/* Initialize to 0 to use both in disable label (ret != 0) and off. */
-	int ret = 0;
+	int ret;
 
 	if (!source_subdev)
 		return -ENODEV;
 
 	if (!on) {
-		v4l2_subdev_call(source_subdev, video, s_stream, 0);
+		ret = v4l2_subdev_call(source_subdev, video, s_stream, 0);
 		goto disable;
 	}
 
···
 	return 0;
 
 disable:
+	if (!on)
+		ret = 0;
 	phy_power_off(dphy);
 	sun8i_a83t_mipi_csi2_disable(csi2_dev);