[Memory] Invalidate physical memory in Release/Decommit (#1559)

src/xenia/memory.h

@@ -392,7 +392,9 @@ class Memory {
   //
   // May be triggered for a single page (in case of a write access violation or
   // when need to synchronize data given by data providers) or for multiple
-  // pages (like when memory is allocated).
+  // pages (like when memory is released, or explicitly to trigger callbacks
+  // when host-side code can't rely on regular access violations, like when
+  // accessing a file).
   //
   // Since granularity of callbacks is one single page, an invalidation
   // notification handler must invalidate the all the data stored in the touched