xwayland: Send ei_device_frame on device_scroll_discrete
This fixes the scroll action in Steam Input in SteamOS/Gamescope when using the new libeis backend. Fixes: a1333342 ("xwayland: Add XTEST support using EIS") Signed-off-by:Joshua Ashton <joshua@froggi.es> (cherry picked from commit 7745fde2) Part-of: <!1533>