BCM2835 PM (Power domains, watchdog)

The PM block controls power domains and some reset lines, and includes
a watchdog timer.  This binding supersedes the brcm,bcm2835-pm-wdt
binding which covered some of PM's register range and functionality.

Required properties:

- compatible:		Should be "brcm,bcm2835-pm"
- reg:			Specifies base physical address and size of the two
			  register ranges ("PM" and "ASYNC_BRIDGE" in that
			  order)
- clocks:		a) v3d: The V3D clock from CPRMAN
			b) peri_image: The PERI_IMAGE clock from CPRMAN
			c) h264: The H264 clock from CPRMAN
			d) isp: The ISP clock from CPRMAN
- #reset-cells: 	Should be 1.  This property follows the reset controller
			  bindings[1].
- #power-domain-cells:	Should be 1.  This property follows the power domain
			  bindings[2].

Optional properties:

- timeout-sec:		Contains the watchdog timeout in seconds
- system-power-controller: Whether the watchdog is controlling the
    system power.  This node follows the power controller bindings[3].

[1] Documentation/devicetree/bindings/reset/reset.txt
[2] Documentation/devicetree/bindings/power/power-domain.yaml
[3] Documentation/devicetree/bindings/power/power-controller.txt

Example:

pm {
	compatible = "brcm,bcm2835-pm", "brcm,bcm2835-pm-wdt";
	#power-domain-cells = <1>;
	#reset-cells = <1>;
	reg = <0x7e100000 0x114>,
	      <0x7e00a000 0x24>;
	clocks = <&clocks BCM2835_CLOCK_V3D>,
		 <&clocks BCM2835_CLOCK_PERI_IMAGE>,
		 <&clocks BCM2835_CLOCK_H264>,
		 <&clocks BCM2835_CLOCK_ISP>;
	clock-names = "v3d", "peri_image", "h264", "isp";
	system-power-controller;
};