NXP LED segment driver devicetree bindings

Required properties:

 - compatible               : "nxp,pca9956b" for PCA9956b
 - nxp,mode1                : MODE1 register
 - nxp,mode2                : MODE2 register
 - nxp,ledout0~5            : LED output state registers
 - nxp,defaultiref          : LED output gain control default value

LED sub-node properties:
 - reg: number of LED line, 0 to 24
 - label: (optional) name of LED
 - linux,default-trigger : (optional)

Example:
pca9956b {
	/* I2C version */
	reg = <0x7d>;

	/* nxp-ledseg properties */

	compatible    = "nxp,pca9956b";

	pinctrl-names = "default";
	pinctrl-0     = <&pca9956b_pins>;

	pca9956b,support_initialize = <1>;
	pca9956b,mode1 = <0x09>;
	pca9956b,mode2 = <0x05>;

	pca9956b,ledout0 = <0xaa>;
	pca9956b,ledout1 = <0xaa>;
	pca9956b,ledout2 = <0xaa>;
	pca9956b,ledout3 = <0xff>;
	pca9956b,ledout4 = <0xff>;
	pca9956b,ledout5 = <0xff>;
	pca9956b,defaultiref = <0x2f>;

	out0@0 {
		label = "ledsec1_b";
		reg = <0x0>;
	};

	out1@1 {
		label = "ledsec1_g";
		reg = <0x1>;
	};

	out5@5 {
		label = "ledsec1_g";
		reg = <0x5>;
		linux,default_trigger = "heartbeat";
	};
};