xwayland: fix -noTouchPointerEmulation

Passing -noTouchPointerEmulation results in an error about the flag not being recognized.

Signed-off-by: Simon Ser contact@emersion.fr Fixes: 7d34b1f2 ("xwayland: add -noTouchPointerEmulation")

cc @whot: Sorry, I'm not sure why the original patch was missing this, it was likely lost in a rebase or refactoring.