Rename leds internal interface led_set_brightness() to __led_set_brightness()
to reduce confusion between led_set_brightness() and the external interface
led_brightness_set(). led_brightness_set() cancels the timer and then calls
led_set_brightness().
Signed-off-by: NShuah Khan <shuahkhan@gmail.com>
Signed-off-by: NBryan Wu <bryan.wu@canonical.com>