This device also requires a voltage regulator which
should be defined in a board-specific maner. An example
dts snipped follows.

/ {
	fixedregulator1v8: fixedregulator@0 {
		compatible = "regulator-fixed";
		regulator-name = "fixed-1.8V";
		regulator-min-microvolt = <1800000>;
		regulator-max-microvolt = <1800000>;
	};
};

&mmcif {
	vmmc-supply = <&fixedregulator1v8>;
	vqmmc-supply = <&fixedregulator1v8>;
};

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>