SMI (Smart Multimedia Interface) Common

The hardware block diagram please check bindings/iommu/mediatek,iommu.txt

Required properties:
- compatible : must be "mediatek,mt8173-smi-common"
- reg : the register and size of the SMI block.
- power-domains : a phandle to the power domain of this local arbiter.
- clocks : Must contain an entry for each entry in clock-names.
- clock-names : must contain 2 entries, as follows:
  - "apb" : Advanced Peripheral Bus clock, It's the clock for setting
	    the register.
  - "smi" : It's the clock for transfer data and command.
  They may be the same if both source clocks are the same.

Example:
	smi_common: smi@14022000 {
		compatible = "mediatek,mt8173-smi-common";
		reg = <0 0x14022000 0 0x1000>;
		power-domains = <&scpsys MT8173_POWER_DOMAIN_MM>;
		clocks = <&mmsys CLK_MM_SMI_COMMON>,
			 <&mmsys CLK_MM_SMI_COMMON>;
		clock-names = "apb", "smi";
	};
