dt-bindings, EDAC: Add Aspeed AST2500

Aspeed AST2500 SoC EDAC node

The Aspeed AST2500 SoC supports DDR3 and DDR4 memory with and without ECC (error

correction check).

The memory controller supports SECDED (single bit error correction, double bit

error detection) and single bit error auto scrubbing by reserving 8 bits for

every 64 bit word (effectively reducing available memory to 8/9).

Note, the bootloader must configure ECC mode in the memory controller.

Required properties:

- compatible: should be "aspeed,ast2500-sdram-edac"

- reg:        sdram controller register set should be <0x1e6e0000 0x174>

- interrupts: should be AVIC interrupt #0

Example:

	edac: sdram@1e6e0000 {

		compatible = "aspeed,ast2500-sdram-edac";

		reg = <0x1e6e0000 0x174>;

		interrupts = <0>;

	};