drm/panel: sony-acx565akm: Use backlight helpers

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.

Instead of manually checking the power state in struct
backlight_properties, use backlight_is_blank().

While we're at it, drop .fb_blank from the initialisation function; it
is deprecated, and this helps make progress towards enabling its
removal. This change makes no functional difference since
FB_BLANK_UNBLANK is the default value.

Signed-off-by: Stephen Kitt <[e-mail]>
Reviewed-by: Sebastian Reichel <[e-mail]>
Cc: Thierry Reding <[e-mail]>
Cc: Sam Ravnborg <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: [e-mail]
Signed-off-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/panel/panel-sony-acx565akm.c

···
 static int acx565akm_bl_update_status_locked(struct backlight_device *dev)
 {
 	struct acx565akm_panel *lcd = dev_get_drvdata(&dev->dev);
-	int level;
-
-	if (dev->props.fb_blank == FB_BLANK_UNBLANK &&
-	    dev->props.power == FB_BLANK_UNBLANK)
-		level = dev->props.brightness;
-	else
-		level = 0;
+	int level = backlight_get_brightness(dev);
 
 	acx565akm_set_brightness(lcd, level);
 
···
 
 	mutex_lock(&lcd->mutex);
 
-	if (dev->props.fb_blank == FB_BLANK_UNBLANK &&
-	    dev->props.power == FB_BLANK_UNBLANK)
+	if (!backlight_is_blank(dev))
 		intensity = acx565akm_get_actual_brightness(lcd);
 	else
 		intensity = 0;
···
 static int acx565akm_backlight_init(struct acx565akm_panel *lcd)
 {
 	struct backlight_properties props = {
-		.fb_blank = FB_BLANK_UNBLANK,
 		.power = FB_BLANK_UNBLANK,
 		.type = BACKLIGHT_RAW,
 	};