Freescale MXS PWM controller

Required properties:
- compatible: should be "fsl,imx23-pwm"
- reg: physical base address and length of the controller's registers
- #pwm-cells: should be 3. See pwm.yaml in this directory for a description of
  the cells format.
- fsl,pwm-number: the number of PWM devices

Example:

pwm: pwm@80064000 {
	compatible = "fsl,imx28-pwm", "fsl,imx23-pwm";
	reg = <0x80064000 0x2000>;
	#pwm-cells = <3>;
	fsl,pwm-number = <8>;
};