PCI Endpoint Function Bus

This describes the bindings for endpoint function bus to which endpoint
function devices should be attached.

Required Properties:
 - compatible: Should be "pci-epf-bus"

One or more subnodes representing PCIe endpoint function device exposed
to the remote host.

Example:
Following is an example of NTB device exposed to the remote host.

epf_bus {
	compatible = "pci-epf-bus";

	ntb {
		compatible = "pci-epf-ntb";
		epcs = <&pcie0_ep>, <&pcie1_ep>;
		epc-names = "primary", "secondary";
		vendor-id = /bits/ 16 <0x104c>;
		device-id = /bits/ 16 <0xb00d>;
		num-mws = <4>;
		mws-size = <0x100000>, <0x100000>, <0x100000>, <0x100000>;
	};
};
