soc/intel/common: Clean up includes

Change-Id: I0081fcf3c842d8772a7045f8dc5754a2e6c039b8
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68702
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>

src/soc/intel/common/vbt.c

@@ -2,9 +2,10 @@
 
 #include <acpi/acpi.h>
 #include <bootmode.h>
+#include <drivers/intel/gma/opregion.h>
+#include <stddef.h>
 
 #include "vbt.h"
-#include <drivers/intel/gma/opregion.h>
 
 void *vbt_get(void)
 {