mtd: mchp23k256: Add OF device ID table

* MTD SPI driver for Microchip 23K256 (and similar) serial SRAM

Required properties:

- #address-cells, #size-cells : Must be present if the device has sub-nodes

  representing partitions.

- compatible : Must be "microchip,mchp23k256"

- reg : Chip-Select number

- spi-max-frequency : Maximum frequency of the SPI bus the chip can operate at

Example:

	spi-sram@0 {

		#address-cells = <1>;

		#size-cells = <1>;

		compatible = "microchip,mchp23k256";

		reg = <0>;

		spi-max-frequency = <20000000>;

	};

#include <linux/sizes.h>

#include <linux/spi/flash.h>

#include <linux/spi/spi.h>

#include <linux/of_device.h>

struct mchp23k256_flash {

	struct spi_device	*spi;

	return mtd_device_unregister(&flash->mtd);

}

static const struct of_device_id mchp23k256_of_table[] = {

	{ .compatible = "microchip,mchp23k256" },

	{}

};

MODULE_DEVICE_TABLE(of, mchp23k256_of_table);

static struct spi_driver mchp23k256_driver = {

	.driver = {

		.name	= "mchp23k256",

		.of_match_table = of_match_ptr(mchp23k256_of_table),

	},

	.probe		= mchp23k256_probe,

	.remove		= mchp23k256_remove,