driver: Add note about checking if _bl_get_brightness actually works

Author: stephan-gh

driver.py

@@ -285,6 +285,8 @@ def generate_backlight(p: Panel, options: Options) -> str:
 	return 0;
 }}
 
+// TODO: Check if /sys/class/backlight/.../actual_brightness actually returns
+// correct values. If not, remove this function.
 static int {p.short_id}_bl_get_brightness(struct backlight_device *bl)
 {{
 	struct mipi_dsi_device *dsi = bl_get_data(bl);