mb/x/acpi_tables: Do minor cleanup on includes

Change-Id: I7a6ddf95d085490d52e00ade7bac23e8c8849427
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42865
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/intel/harcuvar/acpi_tables.c

@@ -8,8 +8,6 @@
 #include <soc/acpi.h>
 #include <soc/nvs.h>
 
-extern const unsigned char AmlCode[];
-
 void acpi_create_gnvs(struct global_nvs *gnvs)
 {
 	acpi_init_gnvs(gnvs);