[U-Boot] rockchip: Set up default PWM flags

[Philipp Tomsich]

> At present if the PWM set_invert() method is not called then the flags are
> not set up and the driver does not work properly. Fix this by setting up
> the default flags when probing.
> 
> Signed-off-by: Simon Glass <sjg at chromium.org>
> Fixes: 874ee59 (rockchip: pwm: implement pwm_set_invert())
> ---
> 
>  drivers/pwm/rk_pwm.c | 1 +
>  1 file changed, 1 insertion(+)
> 

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>