macintosh/via-pmu-backlight: Use backlight helper

backlight_properties.fb_blank is deprecated. The states it represents
are handled by other properties; but instead of accessing those
properties directly, drivers should use the helpers provided by
backlight.h.

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 <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/macintosh/via-pmu-backlight.c

···
 static int __pmu_backlight_update_status(struct backlight_device *bd)
 {
 	struct adb_request req;
-	int level = bd->props.brightness;
-
-
-	if (bd->props.power != FB_BLANK_UNBLANK ||
-	    bd->props.fb_blank != FB_BLANK_UNBLANK)
-		level = 0;
+	int level = backlight_get_brightness(bd);
 
 	if (level > 0) {
 		int pmulevel = pmu_backlight_get_level_brightness(level);