mx6cuboxi: migrate to DM_SERIAL

Add the needed DT overrides to enable UART in SPL.

Cc: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Tested-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>

arch/arm/dts/imx6qdl-hummingboard2-emmc-som-v15-u-boot.dtsi

@@ -15,6 +15,22 @@
 	};
 };
 
+&soc {
+	u-boot,dm-pre-reloc;
+};
+
+&aips1 {
+	u-boot,dm-pre-reloc;
+};
+
+&pinctrl_microsom_uart1 {
+	u-boot,dm-pre-reloc;
+};
+
+&uart1 {
+	u-boot,dm-pre-reloc;
+};
+
 &gpio2 {
 	u-boot,dm-pre-reloc;
 };