backlight: pwm_bl: Set scale type for CIE 1931 curves

For backlight curves calculated with the CIE 1931 algorithm set
the brightness scale type to non-linear. This makes the scale type
available to userspace via the 'scale' sysfs attribute.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/video/backlight/pwm_bl.c

@@ -536,6 +536,8 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 		goto err_alloc;
 	}
 
+	memset(&props, 0, sizeof(struct backlight_properties));
+
 	if (data->levels) {
 		/*
 		 * For the DT case, only when brightness levels is defined
@@ -574,6 +576,8 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 
 			pb->levels = data->levels;
 		}
+
+		props.scale = BACKLIGHT_SCALE_NON_LINEAR;
 	} else {
 		/*
 		 * That only happens for the non-DT case, where platform data
@@ -584,7 +588,6 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 
 	pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
 
-	memset(&props, 0, sizeof(struct backlight_properties));
 	props.type = BACKLIGHT_RAW;
 	props.max_brightness = data->max_brightness;
 	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,