uboot-imx

DM: serial: ti_omap3_common: Don't define serial unless !DM_SERIAL

The serial port was being manually configured during SPL build,
however in preparation to allow DM in SPL, this needs to change
to be based on whether or not DM_SERIAL is enabled because, soon
the assumption that SPL means no DM may not be accurate.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>