NXP Layerscape PCIe Gen4 controller

This PCIe controller is based on the Mobiveil PCIe IP and thus inherits all
the common properties defined in mobiveil-pcie.txt.

Required properties:
- compatible: should contain the platform identifier such as:
  "fsl,lx2160a-pcie"
- reg: base addresses and lengths of the PCIe controller register blocks.
  "csr_axi_slave": Bridge config registers
  "config_axi_slave": PCIe controller registers
- interrupts: A list of interrupt outputs of the controller. Must contain an
  entry for each entry in the interrupt-names property.
- interrupt-names: It could include the following entries:
  "intr": The interrupt that is asserted for controller interrupts
  "aer": Asserted for aer interrupt when chip support the aer interrupt with
	 none MSI/MSI-X/INTx mode,but there is interrupt line for aer.
  "pme": Asserted for pme interrupt when chip support the pme interrupt with
	 none MSI/MSI-X/INTx mode,but there is interrupt line for pme.
- dma-coherent: Indicates that the hardware IP block can ensure the coherency
  of the data transferred from/to the IP block. This can avoid the software
  cache flush/invalid actions, and improve the performance significantly.
- msi-parent : See the generic MSI binding described in
  Documentation/devicetree/bindings/interrupt-controller/msi.txt.

Example:

	pcie@3400000 {
		compatible = "fsl,lx2160a-pcie";
		reg = <0x00 0x03400000 0x0 0x00100000   /* controller registers */
		       0x80 0x00000000 0x0 0x00001000>; /* configuration space */
		reg-names = "csr_axi_slave", "config_axi_slave";
		interrupts = <GIC_SPI 108 IRQ_TYPE_LEVEL_HIGH>, /* AER interrupt */
			     <GIC_SPI 108 IRQ_TYPE_LEVEL_HIGH>, /* PME interrupt */
			     <GIC_SPI 108 IRQ_TYPE_LEVEL_HIGH>; /* controller interrupt */
		interrupt-names = "aer", "pme", "intr";
		#address-cells = <3>;
		#size-cells = <2>;
		device_type = "pci";
		apio-wins = <8>;
		ppio-wins = <8>;
		dma-coherent;
		bus-range = <0x0 0xff>;
		msi-parent = <&its>;
		ranges = <0x82000000 0x0 0x40000000 0x80 0x40000000 0x0 0x40000000>;
		#interrupt-cells = <1>;
		interrupt-map-mask = <0 0 0 7>;
		interrupt-map = <0000 0 0 1 &gic 0 0 GIC_SPI 109 IRQ_TYPE_LEVEL_HIGH>,
				<0000 0 0 2 &gic 0 0 GIC_SPI 110 IRQ_TYPE_LEVEL_HIGH>,
				<0000 0 0 3 &gic 0 0 GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>,
				<0000 0 0 4 &gic 0 0 GIC_SPI 112 IRQ_TYPE_LEVEL_HIGH>;
	};