Include boot_cpu.c for romstage builds

ROMCC boards were left unmodified.

Change-Id: I3d842196b3f5b6999b6891b914036e9ffcc3cef0
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/3853
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/mainboard/emulation/qemu-i440fx/romstage.c

@@ -29,7 +29,7 @@
 #include <timestamp.h>
 #include "drivers/pc80/udelay_io.c"
 #include "lib/delay.c"
-#include "cpu/x86/lapic/boot_cpu.c"
+#include "cpu/x86/lapic.h"
 
 #include "memory.c"
 

src/mainboard/emulation/qemu-q35/romstage.c

@@ -30,7 +30,7 @@
 #include <timestamp.h>
 #include "drivers/pc80/udelay_io.c"
 #include "lib/delay.c"
-#include "cpu/x86/lapic/boot_cpu.c"
+#include "cpu/x86/lapic.h"
 
 #include "../qemu-i440fx/memory.c"