asus/{p2b-x,p3b-f},intel/i440bx: Move mainboard_romstage_entry()

Change-Id: I3598f548c2d122906fda09c85b5a1c82b0da993b
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38255
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/northbridge/intel/i440bx/Makefile.inc b/src/northbridge/intel/i440bx/Makefile.inc
index 355d9b2..5702585 100644
--- a/src/northbridge/intel/i440bx/Makefile.inc
+++ b/src/northbridge/intel/i440bx/Makefile.inc
@@ -19,6 +19,7 @@
 ramstage-y += northbridge.c
 
 romstage-y += raminit.c
+romstage-y += romstage.c
 romstage-$(CONFIG_DEBUG_RAM_SETUP) += debug.c
 romstage-y += memmap.c