imx: mx6sxsabreauto: select DM_SERIAL

Select DM_SERIAL

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/dts/imx6sx-sabreauto-u-boot.dtsi b/arch/arm/dts/imx6sx-sabreauto-u-boot.dtsi
index 549461d..7812aa3 100644
--- a/arch/arm/dts/imx6sx-sabreauto-u-boot.dtsi
+++ b/arch/arm/dts/imx6sx-sabreauto-u-boot.dtsi
@@ -14,3 +14,7 @@
 		compatible = "jedec,spi-nor";
 	};
 };
+
+&pinctrl_uart1 {
+	u-boot,dm-pre-reloc;
+};