OMAP PRM instance bindings

Power and Reset Manager is an IP block on OMAP family of devices which
handle the power domains and their current state, and provide reset
handling for the domains and/or separate IP blocks under the power domain
hierarchy.

Required properties:
- compatible:	Must contain one of the following:
		"ti,am3-prm-inst"
		"ti,am4-prm-inst"
		"ti,omap4-prm-inst"
		"ti,omap5-prm-inst"
		"ti,dra7-prm-inst"
		and additionally must contain:
		"ti,omap-prm-inst"
- reg:		Contains PRM instance register address range
		(base address and length)

Optional properties:
- #reset-cells:	Should be 1 if the PRM instance in question supports resets.

Example:

prm_dsp2: prm@1b00 {
	compatible = "ti,dra7-prm-inst", "ti,omap-prm-inst";
	reg = <0x1b00 0x40>;
	#reset-cells = <1>;
};