drop half an uart8250 implementation from smiutil and use the common code

drop half an uart8250 implementation from smiutil and use the common code
for that instead. This also allows using non-uart8250 consoles for smi
debugging.

Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Acked-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@6501 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1