Following similar reasoning as commit:
d304331
superio/fintek/f81865f: Avoid .c includes
Avoid any mistaken future inclusion of early_serial.c in mainboard.c
code by providing symbols in romstage.
Change-Id: I9e763a7ad9de090e35acdcf4d6a280d8227c6015
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5508
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>