arm64: dts: qcom: pmk8550: Add PWM controller

arm64: dts: qcom: pmk8550: Add PWM controller

Add the PWM function to the pmk8550 dtsi, which is usually used
to control PWM backlight on platforms using this PMIC.

Signed-off-by: Xilin Wu <wuxilin123@gmail.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260207-pmk8550-pwm-v1-1-f2b26ab98d8b@gmail.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>