[PATCH] backlight: pwm_bl: Do not make the regulator mandatory

[Marek Vasut]

Dear Fabio Estevam,

> Commit 22ceeee1 (pwm-backlight: Add power supply support) caused breakage
> on boards that do not define the backlight regulator on their dts files.
> 
> Instead of making the backlight regulator mandatory, treat it as optional
> instead, so that we do not have breakage.
> 
> This avoids the need for adding a dummy regulator on every dts file that
> uses the pwm-backlight.
> 
> Tested on a mx6qsabresd.

This patch certainly makes sense, there are plenty of simple boards that have no 
actual supply for the PWM.

Acked-by: Marek Vasut <marex at denx.de>

Best regards,
Marek Vasut