spi based seps525 framebuffer display driver

Driver for seps525 display controller (in spi mode), This binding supports selection
of spi chipselect, spi max frequency, gpio to drive dc and reset pin of seps525
controller and spi transaction bit length.

Required properties:
- compatible: "syncoam,seps525"
- reg: Specifies the chip-select the seps525 is connected to on the spi bus
- reset-gpios: gpio connected to reset pin of seps525 controller.
- dc-gpios: gpio connected to dc pin of seps525 controller:
- buswidth: bitlength of each spi transaction

Example:
	displayspi@0 {
		compatible = "syncoam,seps525";
		reg = <0>;
		spi-max-frequency = <10000000>;
		spi-cpol;
		spi-cpha;
		buswidth = <8>;
		reset-gpios = <&gpio 0x1c GPIO_ACTIVE_LOW>;
		dc-gpios = <&gpio 0x1b GPIO_ACTIVE_HIGH>;
	};