* Synopsis Designware PCIe interface

Required properties:
- compatible: should contain "snps,dw-pcie" to identify the
	core, plus an identifier for the specific instance, such
	as "samsung,exynos5440-pcie".
- reg: base addresses and lengths of the pcie controller,
	the phy controller, additional register for the phy controller.
- interrupts: interrupt values for level interrupt,
	pulse interrupt, special interrupt.
- clocks: from common clock binding: handle to pci clock.
- clock-names: from common clock binding: should be "pcie" and "pcie_bus".
- #address-cells: set to <3>
- #size-cells: set to <2>
- device_type: set to "pci"
- ranges: ranges for the PCI memory and I/O regions
- #interrupt-cells: set to <1>
- interrupt-map-mask and interrupt-map: standard PCI properties
	to define the mapping of the PCIe interface to interrupt
	numbers.
- reset-gpio: gpio pin number of power good signal

Example:

SoC specific DT Entry:

	pcie@290000 {
		compatible = "samsung,exynos5440-pcie", "snps,dw-pcie";
		reg = <0x290000 0x1000
			0x270000 0x1000
			0x271000 0x40>;
		interrupts = <0 20 0>, <0 21 0>, <0 22 0>;
		clocks = <&clock 28>, <&clock 27>;
		clock-names = "pcie", "pcie_bus";
		#address-cells = <3>;
		#size-cells = <2>;
		device_type = "pci";
		ranges = <0x00000800 0 0x40000000 0x40000000 0 0x00001000   /* configuration space */
			  0x81000000 0 0	  0x40001000 0 0x00010000   /* downstream I/O */
			  0x82000000 0 0x40011000 0x40011000 0 0x1ffef000>; /* non-prefetchable memory */
		#interrupt-cells = <1>;
		interrupt-map-mask = <0 0 0 0>;
		interrupt-map = <0x0 0 &gic 53>;
	};

	pcie@2a0000 {
		compatible = "samsung,exynos5440-pcie", "snps,dw-pcie";
		reg = <0x2a0000 0x1000
			0x272000 0x1000
			0x271040 0x40>;
		interrupts = <0 23 0>, <0 24 0>, <0 25 0>;
		clocks = <&clock 29>, <&clock 27>;
		clock-names = "pcie", "pcie_bus";
		#address-cells = <3>;
		#size-cells = <2>;
		device_type = "pci";
		ranges = <0x00000800 0 0x60000000 0x60000000 0 0x00001000   /* configuration space */
			  0x81000000 0 0	  0x60001000 0 0x00010000   /* downstream I/O */
			  0x82000000 0 0x60011000 0x60011000 0 0x1ffef000>; /* non-prefetchable memory */
		#interrupt-cells = <1>;
		interrupt-map-mask = <0 0 0 0>;
		interrupt-map = <0x0 0 &gic 56>;
	};

Board specific DT Entry:

	pcie@290000 {
		reset-gpio = <&pin_ctrl 5 0>;
	};

	pcie@2a0000 {
		reset-gpio = <&pin_ctrl 22 0>;
	};
