arm64: dts: rockchip: Remove non-existing pwm-delay-us property

There is neither a driver that parses this nor a DT binding schema that
documents it, so let's remove from the DTS files that make use of this.

The properties that exist are post-pwm-on-delay-ms and pwm-off-delay-ms,
defined in the pwm-backlight DT binding. If the delays are really needed
then those properties should be used instead.

Brian Norris mentioned though that looking at the first downstream usage
of the pwm-delay-us property for RK3399 Gru systems in ChromiumOS tree,
he couldn't find a spec reference that said that this was really needed.

So perhaps it was unnecessary added and a simple removal would be enough.
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Link: https://lore.kernel.org/r/20230330231924.2404747-1-javierm@redhat.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3368-evb.dtsi

@@ -61,7 +61,6 @@ backlight: backlight {
 		pinctrl-names = "default";
 		pinctrl-0 = <&bl_en>;
 		pwms = <&pwm0 0 1000000 PWM_POLARITY_INVERTED>;
-		pwm-delay-us = <10000>;
 	};
 
 	emmc_pwrseq: emmc-pwrseq {

arch/arm64/boot/dts/rockchip/rk3399-gru-chromebook.dtsi

@@ -198,7 +198,6 @@ backlight: backlight {
 		power-supply = <&pp3300_disp>;
 		pinctrl-names = "default";
 		pinctrl-0 = <&bl_en>;
-		pwm-delay-us = <10000>;
 	};
 
 	gpio_keys: gpio-keys {

arch/arm64/boot/dts/rockchip/rk3399-gru-scarlet.dtsi

@@ -167,7 +167,6 @@ backlight: backlight {
 		pinctrl-names = "default";
 		pinctrl-0 = <&bl_en>;
 		pwms = <&pwm1 0 1000000 0>;
-		pwm-delay-us = <10000>;
 	};
 
 	dmic: dmic {