Amlogic DDR bandwidth drvier

This driver is used to measure DDR bandwidth, it can measure total
bandwidth of DDR, also can configure port in each channel and get
detailed bandwidth for each channel.

Required properties for the root node:
 - compatible: one of "amlogic,ddr-bandwidth-m8b"
		      "amlogic,ddr-bandwidth-gx"
		      "amlogic,ddr-bandwidth-gxl"
		      "amlogic,ddr-bandwidth-gxm"
		      "amlogic,ddr-bandwidth-gxlx"
		      "amlogic,ddr-bandwidth-axg"
		      "amlogic,ddr-bandwidth-g12a"
		      "amlogic,ddr-bandwidth-g12b"
		      "amlogic,ddr-bandwidth-txl"
		      "amlogic,ddr-bandwidth-txlx"
		      "amlogic,ddr-bandwidth-txhd"
		      "amlogic,ddr-bandwidth-tm2"
		      "amlogic,ddr-bandwidth-t7"
		      "amlogic,ddr-bandwidth-t3"
		      "amlogic,ddr-bandwidth-tl1"
		      "amlogic,ddr-bandwidth-a1"
		      "amlogic,ddr-bandwidth-c1"
		      "amlogic,ddr-bandwidth-t5"
		      "amlogic,ddr-bandwidth-t5d"
		      "amlogic,ddr-bandwidth-s4"
		      "amlogic,ddr-bandwidth-sc2"
		      "amlogic,ddr-bandwidth-p1"
		      "amlogic,ddr-bandwidth-t5w"
		      "amlogic,ddr-bandwidth-a5"
 - reg: address and size of registers controlling bandwidth function

Example:

	ddr_bandwidth {
		compatible = "amlogic,ddr-bandwidth-g12a";
		status = "okay";
		reg = <0xff638000 0x100
		       0xff638c00 0x100>;
		interrupts = <0 52 1>;
		interrupt-names = "ddr_bandwidth";
	};
