powerpc/85xx: Add binding for SCFG

Freescale Supplement configuration unit (SCFG)

SCFG is the supplemental configuration unit, that provides SoC specific

configuration and status registers for the chip. Such as getting PEX port

status.

Required properties:

- compatible: should be "fsl,<chip>-scfg"

- reg: should contain base address and length of SCFG memory-mapped

registers

Example:

	scfg: global-utilities@fc000 {

		compatible = "fsl,t1040-scfg";

		reg = <0xfc000 0x1000>;

	};