ARM: imx: imx8mn-evk: enable DM_SERIAL

U-Boot complains that CONFIG_SERIAL is not converted to CONFIG_DM_SERIAL
and gives a deadline before possibly removing the board. Migrate to
DM_SERIAL to fulfill the request.

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>
1 file changed