leds: pwm: Add optional GPIO enable pin support
Add support for optional GPIO-based enable pin control to PWM LED driver.
Some PWM LED driver chips like TPS92380 and LT3743 require a separate
enable signal in addition to PWM control. Implement support for such
GPIO control through the "enable-gpios" device tree property, activating
the pin when LED brightness is non-zero and deactivating it when off.
Tested on i.MX8MP EVK with TPS92380 LED driver chip
Signed-off-by: LI Qingwu <Qing-wu.Li@leica-geosystems.com.cn>
Link: https://patch.msgid.link/20251117054511.730246-2-Qing-wu.Li@leica-geosystems.com.cn
Signed-off-by: Lee Jones <lee@kernel.org>