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/southbridge/amd/agesa/hudson/smihandler.c

@@ -18,6 +18,7 @@
  * SMI handler for Hudson southbridges
  */
 
+#include <arch/io.h>
 #include "hudson.h"
 #include "smi.h"
 

src/southbridge/amd/pi/hudson/smihandler.c

@@ -18,6 +18,7 @@
  * SMI handler for Hudson southbridges
  */
 
+#include <arch/io.h>
 #include "hudson.h"
 #include "smi.h"
 

src/southbridge/amd/sb700/smbus.c

@@ -16,6 +16,7 @@
 #ifndef _SB700_SMBUS_C_
 #define _SB700_SMBUS_C_
 
+#include <arch/io.h>
 #include "smbus.h"
 
 extern uint8_t amd_sb700_aux_smbus;

src/southbridge/amd/sb800/smbus.c

@@ -16,6 +16,7 @@
 #ifndef _SB800_SMBUS_C_
 #define _SB800_SMBUS_C_
 
+#include <arch/io.h>
 #include "smbus.h"
 
 static int smbus_wait_until_ready(u32 smbus_io_base)