leds: allow led-drivers to use a variable range of brightness values

This patch allows drivers to override the default maximum brightness value
of 255.  We take care to preserve backwards-compatibility as much as
possible, so that user-space ABI doesn't change for existing drivers.
LED trigger code has also been updated to use the per-LED maximum.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>
diff --git a/drivers/leds/ledtrig-timer.c b/drivers/leds/ledtrig-timer.c
index 3d65313..3b83406 100644
--- a/drivers/leds/ledtrig-timer.c
+++ b/drivers/leds/ledtrig-timer.c
@@ -166,7 +166,7 @@
 
 	timer_data->brightness_on = led_get_brightness(led_cdev);
 	if (timer_data->brightness_on == LED_OFF)
-		timer_data->brightness_on = LED_FULL;
+		timer_data->brightness_on = led_cdev->max_brightness;
 	led_cdev->trigger_data = timer_data;
 
 	init_timer(&timer_data->timer);