Amlogic SPI Flash Controller

Required properties:
- compatible : Should be "amlogic,aml-spi-nor"
- reg : Offset and range of the register set for the controller device, different value for different IC.
- clocks : Handle to spi-nor flash controller clock, please refer to IC spec.
- read-capability : read capability of this flash, please refer to flash spec. 0:normal,1:fast,2:dual read,3:quad read.
- spifc-io-width : the io number of spifc on the board.
- cs_gpios : we use cs pin as gpio.

Example:
spifc: spifc@c1108c80 {
	status = "disabled";
	compatible = "amlogic,aml-spi-nor";
	reg = <0x0 0xc1108c80 0x0 0x80>;
	pinctrl-names = "default";
	pinctrl-0 = <&spifc_all_pins>;
	clocks = <&clkc CLKID_CLK81>;
	clock-names = "core";
	spi-nor@0 {
		compatible = "jedec,spi-nor";
		spifc-frequency = <40000000>;
		read-capability = <2>;
		spifc-io-width = <2>;
		cs_gpios = <&gpio BOOT_11 GPIO_ACTIVE_HIGH>;
	};
};