AGESA fam10: Add missing include

The file is used for fam15.

Change-Id: I7cdf238a8f7be4bf79546bcfc3c9d05bd8986e3e
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/18635
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc@marcjonesconsulting.com>

src/northbridge/amd/agesa/family10/reset_test.h

@@ -18,6 +18,7 @@
 #ifndef _RESET_TEST_H_
 #define _RESET_TEST_H_
 
+#include <arch/io.h>
 #include "amdfam10.h"	/* NODE_PCI */
 
 #define NODE_ID			0x60