Hisilicon hix5hd2 gmac controller

Required properties:
- compatible: should contain one of the following SoC strings:
	* "hisilicon,hix5hd2-gmac"
	* "hisilicon,hi3798cv200-gmac"
	* "hisilicon,hi3516a-gmac"
	and one of the following version string:
	* "hisilicon,hisi-gmac-v1"
	* "hisilicon,hisi-gmac-v2"
  The version v1 includes SoCs hix5hd2.
  The version v2 includes SoCs hi3798cv200, hi3516a.
- reg: specifies base physical address(s) and size of the device registers.
  The first region is the MAC register base and size.
  The second region is external interface control register.
- interrupts: should contain the MAC interrupt.
- #address-cells: must be <1>.
- #size-cells: must be <0>.
- phy-mode: see ethernet.txt [1].
- phy-handle: see ethernet.txt [1].
- clocks: clock phandle and specifier pair.
- clock-names: contain the clock name "mac_core"(required) and "mac_ifc"(optional).
- resets: should contain the phandle to the MAC core reset signal(optional),
	the MAC interface reset signal(optional)
	and the PHY reset signal(optional).
- reset-names: contain the reset signal name "mac_core"(optional),
	"mac_ifc"(optional) and "phy"(optional).
- hisilicon,phy-reset-delays-us: triplet of delays if PHY reset signal given.
	The 1st cell is reset pre-delay in micro seconds.
	The 2nd cell is reset pulse in micro seconds.
	The 3rd cell is reset post-delay in micro seconds.

The MAC address will be determined using the properties defined in
ethernet.txt[1].

- PHY subnode: inherits from phy binding [2]

[1] Documentation/devicetree/bindings/net/ethernet.txt
[2] Documentation/devicetree/bindings/net/phy.txt

Example:
	gmac0: ethernet@f9840000 {
		compatible = "hisilicon,hi3798cv200-gmac", "hisilicon,hisi-gmac-v2";
		reg = <0xf9840000 0x1000>,<0xf984300c 0x4>;
		interrupts = <0 71 4>;
		#address-cells = <1>;
		#size-cells = <0>;
		phy-mode = "rgmii";
		phy-handle = <&phy2>;
		mac-address = [00 00 00 00 00 00];
		clocks = <&crg HISTB_ETH0_MAC_CLK>, <&crg HISTB_ETH0_MACIF_CLK>;
		clock-names = "mac_core", "mac_ifc";
		resets = <&crg 0xcc 8>, <&crg 0xcc 10>, <&crg 0xcc 12>;
		reset-names = "mac_core", "mac_ifc", "phy";
		hisilicon,phy-reset-delays-us = <10000 10000 30000>;

		phy2: ethernet-phy@2 {
			reg = <2>;
		};
	};
