* NXP Flex Serial Peripheral Interface (FSPI)

Required properties:
  - compatible : Should be "nxp,lx2160a-fspi"
			    "nxp,imx8qxp-fspi"
			    "nxp,imx8mm-fspi"
			    "nxp,imx8mp-fspi"
			    "nxp,imx8dxl-fspi"

  - reg :        First contains the register location and length,
                 Second contains the memory mapping address and length
  - reg-names :  Should contain the resource reg names:
	         - fspi_base: configuration register address space
                 - fspi_mmap: memory mapped address space
  - interrupts : Should contain the interrupt for the device

Required SPI slave node properties:
  - reg :        There are two buses (A and B) with two chip selects each.
                 This encodes to which bus and CS the flash is connected:
                 - <0>: Bus A, CS 0
                 - <1>: Bus A, CS 1
                 - <2>: Bus B, CS 0
                 - <3>: Bus B, CS 1

Example showing the usage of two SPI NOR slave devices on bus A:

fspi0: spi@20c0000 {
	compatible = "nxp,lx2160a-fspi";
	reg = <0x0 0x20c0000 0x0 0x10000>, <0x0 0x20000000 0x0 0x10000000>;
	reg-names = "fspi_base", "fspi_mmap";
	interrupts = <0 25 0x4>; /* Level high type */
	clocks = <&clockgen 4 3>, <&clockgen 4 3>;
	clock-names = "fspi_en", "fspi";

	mt35xu512aba0: flash@0 {
		reg = <0>;
		....
	};

	mt35xu512aba1: flash@1 {
		reg = <1>;
		....
	};
};