ARM: dts: imx6ul: imx6ul-14x14-evk.dtsi: Fix SPI NOR probing

Without this "jedec,spi-nor" compatible property, probing of the SPI NOR
does not work on the NXP i.MX6ULL EVK. Fix this by adding this
compatible property to the DT.

Fixes: 7d77b850 ("ARM: dts: imx6ull: fix the imx6ull-14x14-evk configuration")
Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6ul-14x14-evk.dtsi

@@ -227,7 +227,7 @@ &qspi {
 	flash0: n25q256a@0 {
 		#address-cells = <1>;
 		#size-cells = <1>;
-		compatible = "micron,n25q256a";
+		compatible = "micron,n25q256a", "jedec,spi-nor";
 		spi-max-frequency = <29000000>;
 		spi-rx-bus-width = <4>;
 		spi-tx-bus-width = <4>;