board: gateworks: venice: enable DM_SERIAL

Enable DM_SERIAL.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/configs/imx8mn_venice_defconfig b/configs/imx8mn_venice_defconfig
index c3a96a3..41898da 100644
--- a/configs/imx8mn_venice_defconfig
+++ b/configs/imx8mn_venice_defconfig
@@ -108,6 +108,8 @@
 CONFIG_DM_REGULATOR=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_DM_REGULATOR_GPIO=y
+CONFIG_DM_SERIAL=y
+# CONFIG_SPL_DM_SERIAL is not set
 CONFIG_MXC_UART=y
 CONFIG_SYSRESET=y
 CONFIG_SPL_SYSRESET=y