Brcmstb PCIe Host Controller Device Tree Bindings

Required Properties:
- compatible
  "brcm,bcm7425-pcie" -- for 7425 family MIPS-based SOCs.
  "brcm,bcm7435-pcie" -- for 7435 family MIPS-based SOCs.
  "brcm,bcm7445-pcie" -- for 7445 and later ARM based SOCs (not including
      the 7278).
  "brcm,bcm7278-pcie"  -- for 7278 family ARM-based SOCs.

- reg -- the register start address and length for the PCIe reg block.
- interrupts -- two interrupts are specified; the first interrupt is for
     the PCI host controller and the second is for MSI if the built-in
     MSI controller is to be used.
- interrupt-names -- names of the interrupts (above): "pcie" and "msi".
- #address-cells -- set to <3>.
- #size-cells -- set to <2>.
- #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.
- ranges: ranges for the PCI memory and I/O regions.
- linux,pci-domain -- should be unique per host controller.

Optional Properties:
- clocks -- phandle of pcie clock.
- clock-names -- set to "sw_pcie" if clocks is used.
- dma-ranges -- Specifies the inbound memory mapping regions when
     an "identity map" is not possible.
- msi-controller -- this property is typically specified to have the
     PCIe controller use its internal MSI controller.
- msi-parent -- set to use an external MSI interrupt controller.
- brcm,enable-ssc -- (boolean) indicates usage of spread-spectrum clocking.
- max-link-speed --  (integer) indicates desired generation of link:
     1 => 2.5 Gbps (gen1), 2 => 5.0 Gbps (gen2), 3 => 8.0 Gbps (gen3).

Example Node:

pcie0: pcie@f0460000 {
		reg = <0x0 0xf0460000 0x0 0x9310>;
		interrupts = <0x0 0x0 0x4>;
		compatible = "brcm,bcm7445-pcie";
		#address-cells = <3>;
		#size-cells = <2>;
		ranges = <0x02000000 0x00000000 0x00000000 0x00000000 0xc0000000 0x00000000 0x08000000
			  0x02000000 0x00000000 0x08000000 0x00000000 0xc8000000 0x00000000 0x08000000>;
		#interrupt-cells = <1>;
		interrupt-map-mask = <0 0 0 7>;
		interrupt-map = <0 0 0 1 &intc 0 47 3
				 0 0 0 2 &intc 0 48 3
				 0 0 0 3 &intc 0 49 3
				 0 0 0 4 &intc 0 50 3>;
		clocks = <&sw_pcie0>;
		clock-names = "sw_pcie";
		msi-parent = <&pcie0>;  /* use PCIe's internal MSI controller */
		msi-controller;         /* use PCIe's internal MSI controller */
		brcm,ssc;
		max-link-speed = <1>;
		linux,pci-domain = <0>;
	};