pico-dwarf/hobbit-imx6ul: Convert to CONFIG_DM_SERIAL

The conversion to CONFIG_DM_SERIAL is mandatory, so select
this option.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
diff --git a/configs/pico-dwarf-imx6ul_defconfig b/configs/pico-dwarf-imx6ul_defconfig
index 7ae3726..8b90285 100644
--- a/configs/pico-dwarf-imx6ul_defconfig
+++ b/configs/pico-dwarf-imx6ul_defconfig
@@ -67,6 +67,7 @@
 CONFIG_DM_REGULATOR_PFUZE100=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_DM_REGULATOR_GPIO=y
+CONFIG_DM_SERIAL=y
 CONFIG_MXC_UART=y
 CONFIG_USB=y
 CONFIG_SPL_USB_HOST=y
diff --git a/configs/pico-hobbit-imx6ul_defconfig b/configs/pico-hobbit-imx6ul_defconfig
index fc5a54b..e3aca6e 100644
--- a/configs/pico-hobbit-imx6ul_defconfig
+++ b/configs/pico-hobbit-imx6ul_defconfig
@@ -70,6 +70,7 @@
 CONFIG_DM_REGULATOR_PFUZE100=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_DM_REGULATOR_GPIO=y
+CONFIG_DM_SERIAL=y
 CONFIG_MXC_UART=y
 CONFIG_USB=y
 CONFIG_SPL_USB_HOST=y