GameDatabase: Warn if CPU mode is enabled and unnecessary

src/core/game_database.cpp

@@ -580,6 +580,14 @@ void GameDatabase::Entry::ApplySettings(Settings& settings, bool display_osd_mes
 
     settings.gpu_pgxp_cpu = true;
   }
+  else if (settings.UsingPGXPCPUMode())
+  {
+    Host::AddIconOSDMessage(
+      "gamedb_force_pgxp_cpu", ICON_FA_MICROCHIP,
+      TRANSLATE_STR("OSDMessage",
+                    "PGXP CPU mode is enabled, but it is not required for this game. This may cause rendering errors."),
+      osd_duration);
+  }
 
   if (HasTrait(Trait::DisablePGXPDepthBuffer))
   {