superio/ite/*: Factor out generic romstage component

Following the reasoning of:
cf7b498 superio/fintek/*: Factor out generic romstage component

Change-Id: I4c0a9a5a7786eb8fcb0c3ed6251c7fe9bbbadae7
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5585
Tested-by: build bot (Jenkins)
Reviewed-by: Rudolf Marek <r.marek@assembler.cz>
diff --git a/src/mainboard/soyo/sy-6ba-plus-iii/romstage.c b/src/mainboard/soyo/sy-6ba-plus-iii/romstage.c
index 632a3117..551c060 100644
--- a/src/mainboard/soyo/sy-6ba-plus-iii/romstage.c
+++ b/src/mainboard/soyo/sy-6ba-plus-iii/romstage.c
@@ -30,8 +30,7 @@
 #include "drivers/pc80/udelay_io.c"
 #include "lib/delay.c"
 #include "cpu/x86/bist.h"
-void it8671f_48mhz_clkin(void);
-#include "superio/ite/it8671f/early_serial.c"
+#include <superio/ite/it8671f/it8671f.h>
 #include <lib.h>
 
 #define SERIAL_DEV PNP_DEV(0x370, IT8671F_SP1)