isa: use get_uint() for "io-base"

The property is defined with DEFINE_PROP_UINT32().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170607163635.17635-21-marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

include/hw/isa/isa.h

@@ -29,7 +29,7 @@ static inline uint16_t applesmc_port(void)
     Object *obj = object_resolve_path_type("", TYPE_APPLE_SMC, NULL);
 
     if (obj) {
-        return object_property_get_int(obj, APPLESMC_PROP_IO_BASE, NULL);
+        return object_property_get_uint(obj, APPLESMC_PROP_IO_BASE, NULL);
     }
     return 0;
 }