arm64: dts: ls1028a-rdb: add an alias for the FlexSPI controller

This is used by U-Boot and is required for keeping the device trees in
sync.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/fsl-ls1028a-rdb.dts

@@ -22,6 +22,7 @@ aliases {
 		mmc0 = &esdhc;
 		mmc1 = &esdhc1;
 		rtc1 = &ftm_alarm0;
+		spi0 = &fspi;
 	};
 
 	chosen {