backlight: aat2870: Use backlight helper

Instead of retrieving the backlight brightness in struct
backlight_properties manually, and then checking whether the backlight
should be on at all, use backlight_get_brightness() which does all
this and insulates this from future changes.
Signed-off-by: Stephen Kitt <steve@sk2.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230106164856.1453819-2-steve@sk2.org

drivers/video/backlight/aat2870_bl.c

@@ -59,7 +59,7 @@ static int aat2870_bl_update_status(struct backlight_device *bd)
 	struct aat2870_bl_driver_data *aat2870_bl = bl_get_data(bd);
 	struct aat2870_data *aat2870 =
 			dev_get_drvdata(aat2870_bl->pdev->dev.parent);
-	int brightness = bd->props.brightness;
+	int brightness = backlight_get_brightness(bd);
 	int ret;
 
 	if ((brightness < 0) || (bd->props.max_brightness < brightness)) {
@@ -70,11 +70,6 @@ static int aat2870_bl_update_status(struct backlight_device *bd)
 	dev_dbg(&bd->dev, "brightness=%d, power=%d, state=%d\n",
 		 bd->props.brightness, bd->props.power, bd->props.state);
 
-	if ((bd->props.power != FB_BLANK_UNBLANK) ||
-			(bd->props.state & BL_CORE_FBBLANK) ||
-			(bd->props.state & BL_CORE_SUSPENDED))
-		brightness = 0;
-
 	ret = aat2870->write(aat2870, AAT2870_BLM,
 			     (u8)aat2870_brightness(aat2870_bl, brightness));
 	if (ret < 0)