* AW36518 flash driver support

Required Properties:
- compatible: Must contain "awinic,aw36518"
- reg: I2C slave address
- enable-gpios: Specifier of the GPIO connected to strobe/torch EN pin
this pin is for hardware flash/torch mode, if not, will using i2c control.
- tx-gpio: Specifier of the GPIO connected to TX pin
this pin is synchronization input for RF power Amplifier Pulse Eventr;
if not, will using assist mode.

A discrete LED element connected to the device must be represented by a child
node - see Documentation/devicetree/bindings/leds/common.txt.

Required properties of the LED child node:
- led-max-microamp : see Documentation/devicetree/bindings/leds/common.txt
- flash-max-microamp : see Documentation/devicetree/bindings/leds/common.txt
- flash-max-timeout-us : see Documentation/devicetree/bindings/leds/common.txt

Special properties:
- rockchip,camera-module-index : indicate which camera the flash belongs to.
- rockchip,camera-module-facing : indicate the camera facing.

Example:

&i2c1 {
	...
	aw36518: aw36518@63 {
		#address-cells = <1>;
		#size-cells = <0>;
		compatible = "awinic,aw36518";
		status = "okay";
		reg = <0x63>;
		rockchip,camera-module-index = <0>;
		rockchip,camera-module-facing = "back";
		enable-gpio = <&gpio3 RK_PC3 GPIO_ACTIVE_HIGH>;
		tx-gpio = <&gpio3 RK_PC2 GPIO_ACTIVE_HIGH>;
		aw36518_led0: led@0 {
			reg = <0x0>;
			led-max-microamp = <386000>;
			flash-max-microamp = <1500000>;
			flash-max-timeout-us = <1600000>;
		};
	};
	...
	ov13850: ov13850@10 {
		...
		flash-leds = <&aw36518_led0>;
		...
	};
	...
}