Description:
Qt.labs.platform.Menu on linux content positioning is broken

Steps to reproduce(see attached example):
1. Move main app window to bottom of the screen(see attached screens)
2. Click on the field below the red line(menu is broken, see attached screens)
3. Click above blue line it works as expected (see attached screens)

Actual result:
Menu content starts from clicked point by y axes

Expected result:
Menu content starts from the top of the menu