community/kwin: apply fix for the Librem 5
The Librem 5 is currently broken with Plasma. Interestingly enough the device reports 3 displays even though it really only as 2 (internal and USB-C out) and KWin picks the wrong. Then it tries to do a buffer copy between... the same device...
This patch makes KWin use the right display. Figured out on Akademy with a KWin dev, yay for conferences!