DC based PWM backlight is found on some T20 and T30 devices
(HTC One X). This backlight is controlled by Tegra DC and
is adjustable by the DC PM0 or PM1 signal.
Tested-by: Andreas Westman Dorcsak <hedmoo@yahoo.com> # HTC One X T30
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # HTC One X T30
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
