spi: fsl-qspi: Enhance binding to extend example for flash entry

Add example for adding flash entry on various boards' dts
using flash manufacture spansion/cypress.

Signed-off-by: Ashish Kumar <Ashish.Kumar@nxp.com>
Link: https://lore.kernel.org/r/1565691791-26167-3-git-send-email-Ashish.Kumar@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/spi-fsl-qspi.txt

@@ -34,7 +34,11 @@ qspi0: quadspi@40044000 {
 	clock-names = "qspi_en", "qspi";
 
 	flash0: s25fl128s@0 {
-		....
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "spansion,s25fl128s", "jedec,spi-nor";
+		spi-max-frequency = <50000000>;
+		reg = <0>;
 	};
 };