ARM: dts: imx6qdl-apf6dev: Use #pwm-cells = <3> for imx27-pwm devices

ARM: dts: imx6qdl-apf6dev: Use #pwm-cells = <3> for imx27-pwm devices

The binding dictates using 3 pwm-cells. Adhere to that.

This fixes the following dtbs_check warnings:

	arch/arm/boot/dts/nxp/imx/imx6dl-apf6dev.dtb: pwm@2088000: #pwm-cells:0:0: 3 was expected
		from schema : http://devicetree.org/schemas/pwm/imx-pwm.yaml#
	arch/arm/boot/dts/nxp/imx/imx6q-apf6dev.dtb: pwm@2088000: #pwm-cells:0:0: 3 was expected
		from schema : http://devicetree.org/schemas/pwm/imx-pwm.yaml#

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>