arm64: dts: imx8qxp: add serial alias

Add i.MX8QXP serial alias for lpuart ports.
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8qxp.dtsi

@@ -30,6 +30,9 @@ aliases {
 		mmc2 = &usdhc3;
 		mu1 = &lsio_mu1;
 		serial0 = &adma_lpuart0;
+		serial1 = &adma_lpuart1;
+		serial2 = &adma_lpuart2;
+		serial3 = &adma_lpuart3;
 	};
 
 	cpus {