Debugger: Make peripheral register group menu scrollable

... to save a display space.

Change-Id: I93812bb97538dc88cc6e871a40e1bce6419024c1
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/peripheralregisterhandler.cpp

@@ -799,6 +799,7 @@ QMenu *PeripheralRegisterHandler::createRegisterGroupsMenu(DebuggerState state)
         hasActions = true;
     }
     groupMenu->setEnabled(hasActions);
+    groupMenu->setStyleSheet("QMenu { menu-scrollable: 1; }");
     return groupMenu;
 }