drivers/serial/s3c2410.c: remove dead config symbols

Remove dead config symbol.

Signed-off-by: Jiri Olsa <olsajiri@gmail.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ben Dooks <ben@fluff.org>
Cc: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>