power: supply: max77650: Make max77650_charger_disable() return void

The return value of max77650_charger_disable() is ignored by all but one
caller. That one caller propagates the error code in the platform driver's
remove function. The only effect of that is that the driver core emits
a generic error message (but still removes the device). As
max77650_charger_disable() already emits an error message, this can better
be changed to return zero.

This is a preparation for making struct platform_driver::remove return
void, too.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>