os: add tentative IoRegionType

libraries/libstratosphere/include/stratosphere/os/os_memory_common.hpp

@@ -30,4 +30,7 @@ namespace ams::os {
         MemoryPermission_ReadWrite = MemoryPermission_ReadOnly | MemoryPermission_WriteOnly,
     };
 
+    using MemoryMapping = svc::MemoryMapping;
+    using enum svc::MemoryMapping;
+
 }