wayland: Fix sending wl_pointer.leave event to Xwayland during dnd
The wl_pointer.leave event should be sent only if the entered surface has no data devices associated with it (i.e. it's owned by Xwayland), otherwise Xwayland won't be able to receive new pointer position and the source X drag client won't be able to move the drag icon window.
(cherry picked from commit 0451ac04)
Co-authored-by: Vlad Zahorodnii vlad.zahorodnii@kde.org