arm: mvebu: solidrun-microsom: update SPI flash compatible

Add the "spi-flash" compatible string so that the generic sf_probe
driver can probe the SPI flash on the SolidRun SOM.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Stefan Roese <sr@denx.de>

arch/arm/dts/armada-38x-solidrun-microsom.dtsi

@@ -86,7 +86,7 @@
 	w25q32: spi-flash@0 {
 		#address-cells = <1>;
 		#size-cells = <1>;
-		compatible = "w25q32", "jedec,spi-nor";
+		compatible = "w25q32", "jedec,spi-nor", "spi-flash";
 		reg = <0>; /* Chip select 0 */
 		spi-max-frequency = <3000000>;
 		status = "disabled";