northbridge/intel/i440bx: Unify UDELAY selection

Instead of manually including udelay_io.c in each romstage,
select UDELAY_IO for all i440BX boards in the chipset.

Change-Id: I411191927f3fba1d0749edcf79378e8013fb195a
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/13781
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/drivers/pc80/Makefile.inc

@@ -5,6 +5,7 @@ ramstage-$(CONFIG_DRIVERS_MC146818) += mc146818rtc.c
 ramstage-y += isa-dma.c
 ramstage-y += i8254.c
 ramstage-y += i8259.c
+romstage-$(CONFIG_UDELAY_IO) += udelay_io.c
 ramstage-$(CONFIG_UDELAY_IO) += udelay_io.c
 ramstage-y += keyboard.c
 ramstage-$(CONFIG_SPKMODEM) += spkmodem.c