PBIAS internal regulator for SD card i/o pads on OMAP SoCs.

Required properties:
- compatible:
  - "regulator-pbias-omap2" for OMAP2
  - "regulator-pbias-omap3" for OMAP3
  - "regulator-pbias-omap4" for OMAP4
  - "regulator-pbias-omap5" for OMAP5, DRA7
- pbias-reg-offset: PBIAS control register offset from syscon base address

Optional properties:
- Any optional property defined in bindings/regulator/regulator.txt

Example:

		pbias_regulator: pbias_regulator {
			pbias-reg-offset = <0>;
			regulator-name = "pbias_regulator";
			regulator-min-microvolt = <1800000>;
			regulator-max-microvolt = <3000000>;
	};
