arm64: dts: imx8qm: added more serial alias to dts

Add more serial alias to imx8qm.dtsi file

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Oliver Graute <oliver.graute@kococonnector.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8qm.dtsi

@@ -20,6 +20,9 @@
 		mmc1 = &usdhc2;
 		mmc2 = &usdhc3;
 		serial0 = &lpuart0;
+		serial1 = &lpuart1;
+		serial2 = &lpuart2;
+		serial3 = &lpuart3;
 	};
 
 	cpus {