backlight: mt6370-backlight: Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is (mostly) ignored
and this typically results in resource leaks. To improve here there is a
quest to make the remove callback return void. In the first step of this
quest all drivers are converted to .remove_new() which already returns
void.

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230308073945.2336302-10-u.kleine-koenig@pengutronix.de

video: backlight: mt6370: Add MediaTek MT6370 support

MediaTek MT6370 is a SubPMIC consisting of a single cell battery charger
with ADC monitoring, RGB LEDs, dual channel flashlight, WLED backlight
driver, display bias voltage supply, one general purpose LDO, and the
USB Type-C & PD controller complies with the latest USB Type-C and PD
standards.

Add support for the MediaTek MT6370 backlight driver.
It controls 4 channels of 8 series WLEDs in
2048 (only for MT6370/MT6371) / 16384 (only for MT6372)
current steps (30 mA) in exponential or linear mapping curves.

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: ChiaEn Wu <chiaen_wu@richtek.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220830034042.9354-11-peterwu.pub@gmail.com