imx: mx6sabresd: select DM_SERIAL

Select DM_SERIAL

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/configs/mx6sabresd_defconfig b/configs/mx6sabresd_defconfig
index 9472e03..cae23b9 100644
--- a/configs/mx6sabresd_defconfig
+++ b/configs/mx6sabresd_defconfig
@@ -106,6 +106,7 @@
 CONFIG_DM_REGULATOR=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_POWER_I2C=y
+CONFIG_DM_SERIAL=y
 CONFIG_MXC_UART=y
 CONFIG_SPI=y
 CONFIG_DM_SPI=y