winex11.drv: Fix display name in X11DRV_UpdateDisplayDevices().
For example, when GPU 1 has adapter 1 and GPU 2 has adapter 2, without this fix, the adapter
variable in the for loop is always zero when forming GDI display names \.\DISPLAY* because these
two adapters are on different GPUs. Thus "\.\DISPLAY1" is incorrectly passed to xrandr14_get_id()
for the second adapter and eventually gets the wrong current display mode for the second adapter.