dt-bindings: leds: pwm: Add enable-gpios property

dt-bindings: leds: pwm: Add enable-gpios property

Some PWM LED driver chips like TPS92380 and LT3743 require a separate
enable signal in addition to PWM control. Add this property to allow
device trees to specify such GPIO, which will be controlled
automatically by the driver based on the LED brightness state.

Signed-off-by: LI Qingwu <Qing-wu.Li@leica-geosystems.com.cn>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20251117054511.730246-1-Qing-wu.Li@leica-geosystems.com.cn
Signed-off-by: Lee Jones <lee@kernel.org>