Phytium Multimedia Card Interface controller

The highspeed MMC host controller on Phytium SoCs provides an interface
for MMC, SD and SDIO types of memory cards.

Required properties:
- compatible : should be "phytium,mci".
- reg: mmc controller base registers.
- clocks : phandles to input clocks.
- clock-names : should be "phytium_mci_clk".
- interrupts : mmc controller interrupt.

Examples:
	- Within .dtsi:
	mmc0: mmc@28000000 {
		compatible = "phytium,mci";
		reg = <0x0 0x28000000 0x0 0x1000>;
		interrupts = <GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&sysclk_1200mhz>;
		clock-names = "phytium_mci_clk";
		status = "disabled";
	};

	- Within dts:
	&mmc0 {
		bus-width = <4>;
		max-frequency = <50000000>;
		cap-sdio-irq;
		cap-sd-highspeed;
		sd-uhs-sdr12;
		sd-uhs-sdr25;
		sd-uhs-sdr50;
		no-mmc;
		status = "ok";
	};
