Qualcomm QPNP Leds

QPNP (Qualcomm Plug N Play) LEDs driver is used for
controlling LEDs that are part of PMIC on Qualcomm reference
platforms. The PMIC is connected to Host processor via
SPMI bus. This driver supports various LED modules such as
WLED (white LED), RGB LED and flash LED. The first version of
the driver supports WLED and other features are added in the
next versions.

Required Properties:
- compatible	: should be "qcom,leds-qpnp"

Each LED module is represented as a node of "leds-qpnp". This
node will furthur contain the type of LED supported and its
properties.

Required properties:
- qcom,id		: must be one of values supported in enum qpnp_led
- qcom,label		: type of led that will be used, ie "wled"
- qcom,max-current	: maximum current that the LED can sustain
= qcom,name		: name the led will be called by in sysfs entry

WLED is primarily used as display backlight. Display subsystem uses
LED triggers for WLED to control the brightness as needed.

Optional properties for WLED:
- qcom,num-strings: number of wled strings supported
- qcom,ovp_val: over voltage protection threshold,
		follows enum wled_ovp_threshold
- qcom,boost_curr_lim: boot currnet limit, follows enum wled_current_bost_limit
- qcom,ctrl_delay_us: delay in activation of led
- qcom,dig_mod_gen_en: digital module generator
- qcom,cs_out_en: current sink output enable
- qcom,op_fdbck: selection of output as feedback for the boost
- qcom,cp_select: high pole capacitance
- linux,default-trigger: trigger the led from external modules such as display
- qcom,default-state:  default state of the led, should be "on" or "off"

Example:

	qcom,leds@d800 {
			compatible = "qcom,leds-qpnp";
			reg = <0xD800 0x100>;
			linux,default-trigger = "bkl-trigger"
			qcom,label = "wled";
			qcom,cs-out-en;
			qcom,op-fdbck;
			qcom,default-state "off";
			qcom,max-current = <25>;
			qcom,ctrl-delay-us = <0>;
			qcom,boost-curr-lim = <3>;
			qcom,cp-sel = <0>;
			qcom,switch-freq = <2>;
			qcom,ovp-val = <2>;
			qcom,num-strings = <1>;
	}
