superio/nsc/pc87309: Avoid .c includes in mainboard

Make superio romstage component link-time symbols.

Change-Id: Icde27465a05946498ff7b8f1aaa7a9e8ba074272
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5880
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
4 files changed