Qualcomm Technologies Inc. PWM controller

PDM is used for generating density modulated signals that, after passing
through a filter, become analog signals. It can produce fixed densities
or alternate between densities to create variations in the analog signal.

PWM has the following use:
1) Duty cycle control of the backlight.


Required properties:
- compatible: should be "qcom,pdm-pwm"

- reg: physical base address and length of the controller's registers.

- clocks: clocks required for enabling PWM block.

- #pwm-cells: shall contain 2.

- pwm@<num> : defines pwm instances.

- frame-index : each pwm has 10 frames 0-9 and they are designed to stand by
		themselves independent of the other frame. For this reason,
		each PWM instance has its own set of configuration registers.
- frame-offset: offset of each pwm instance from base.

Example:

	pdm_pwm0: pdm_pwm_test@600000 {
		compatible = "qcom,pdm-pwm";
		reg = <0x600000 0xc000>;
		clocks = <&clock_gcc GCC_PDM_AHB_CLK>,
			<&clock_gcc GCC_PWM0_XO512_CLK>;
		clock-names = "pdm_ahb_clk", "pwm_core_clk";
		#pwm-cells = <2>;

		pwm@0{
			frame-index = <0>;
			frame-offset = <0x1000>;
		};
	};