arm64: zynqmp: Add spi-flash compatible string to flash node

spi-flash compatible string is needed for reading tx and rx bus
widths, hence add this compatible string to flash node.
Signed-off-by: NSiva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>

arch/arm/dts/zynqmp-mini-qspi.dts

@@ -64,7 +64,7 @@
 &qspi {
 	status = "okay";
 	flash@0 {
-		compatible = "n25q512a11";
+		compatible = "n25q512a11", "spi-flash";
 		#address-cells = <1>;
 		#size-cells = <1>;
 		reg = <0x0>;