Qualcomm Quad Serial Peripheral Interface (QSPI)

The QSPI controller allows SPI protocol communication in single, dual, or quad
wire transmission modes for read/write access to slaves such as NOR flash.

Required properties:
- compatible:	An SoC specific identifier followed by "qcom,qspi-v1", such as
		"qcom,sdm845-qspi", "qcom,qspi-v1"
- reg:		Should contain the base register location and length.
- interrupts:	Interrupt number used by the controller.
- clocks:	Should contain the core and AHB clock.
- clock-names:	Should be "core" for core clock and "iface" for AHB clock.

SPI slave nodes must be children of the SPI master node and can contain
properties described in Documentation/devicetree/bindings/spi/spi-bus.txt

Example:

	qspi: spi@88df000 {
		compatible = "qcom,sdm845-qspi", "qcom,qspi-v1";
		reg = <0x88df000 0x600>;
		#address-cells = <1>;
		#size-cells = <0>;
		interrupts = <GIC_SPI 82 IRQ_TYPE_LEVEL_HIGH>;
		clock-names = "iface", "core";
		clocks = <&gcc GCC_QSPI_CNOC_PERIPH_AHB_CLK>,
			 <&gcc GCC_QSPI_CORE_CLK>;

		flash@0 {
			compatible = "jedec,spi-nor";
			reg = <0>;
			spi-max-frequency = <25000000>;
			spi-tx-bus-width = <2>;
			spi-rx-bus-width = <2>;
		};
	};