arch/io.h: Add missing includes

Fixes indirect includes that would break with followup work.

Change-Id: I37ca01b904a0b422a4d09475377e755e167a6ab3
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/31697
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/soc/intel/common/block/smbus/smbus.c

@@ -13,6 +13,7 @@
  * GNU General Public License for more details.
  */
 
+#include <arch/io.h>
 #include <device/device.h>
 #include <device/path.h>
 #include <device/smbus.h>