devicetree binding for Goodix spi touchdriver

Required properties:
 - compatible: device & driver matching.
        * for berlin series touch device, such as "goodix,gt9916S", "goodix,gt9916S2"

 - spi-max-frequency: set spi transfer speed.
 - reg: depend on CS gpio.
 - goodix,reset-gpio: reset gpio.
 - goodix,irq-gpio: interrupt gpio.
 - goodix,irq-flags: irq trigger type config, value should be:
                1 - rising edge,
                2 - falling edge,
                4 - high level,
                5 - low level.
 - goodix,panel-max-x: max resolution of x direction.
 - goodix,panel-max-y: max resolution of y direction.
 - goodix,panel-max-w: panel max width value.
 - goodix,panel-max-p: pen device max pressure value.

Optional properties:
 - goodix,avdd-name: set name of regulator.
 - avdd-supply: power supply for the touch device.
   example of regulator:
        goodix,avdd-name = "avdd";
        avdd-supply = <&pm8916_l15>;
 - iovdd-supply: power supply for digital io circuit
   example of regulator:
        goodix,iovdd-name = "iovdd";
        iovdd-supply = <&pm8916_l16>;
 - goodix,pen-enable: set this property if you want support stylus.
        goodix,pen-enable;
 - goodix,firmware-name: set firmware file name, if not configured, use the default name.
 - goodix,config-name: set config file name, if not configured, use the default name.

Example 1:
	goodix-berlin@0 {
		compatible = "goodix,gt9916S";
		reg = <0>;
		spi-max-frequency = <1000000>;
		goodix,reset-gpio = <&msm_gpio 12 0x0>;
		goodix,irq-gpio = <&msm_gpio 13 0x2800>;
		goodix,irq-flags = <2>; /* 1:trigger rising, 2:trigger falling;*/
		goodix,panel-max-x = <720>;
		goodix,panel-max-y = <1280>;
		goodix,panel-max-w = <255>;
	};

Example 2:
	goodix-berlin@0 {
		compatible = "goodix,gt9916S2";
		reg = <0>;
		spi-max-frequency = <1000000>;

		goodix,avdd-name = "avdd";
		avdd-supply = <&pm8916_l15>;
		goodix,iovdd-name = "iovdd";
		iovdd-supply = <&pm8916_l16>;

		goodix,reset-gpio = <&msm_gpio 12 0x0>;
		goodix,irq-gpio = <&msm_gpio 13 0x2800>;
		goodix,irq-flags = <2>; /* 1:trigger rising, 2:trigger falling;*/
		goodix,panel-max-x = <720>;
		goodix,panel-max-y = <1280>;
		goodix,panel-max-w = <255>;
		goodix,panel-max-p = <4096>; /* max pressure that pen device supported */
		goodix,pen-enable; /* support active stylus device*/

		goodix,firmware-name = "goodix_firmware.bin";
		goodix,config-name = "goodix_cfg_group.bin";
	};