Input: restore EV_ABS ABS_RESERVED

ABS_RESERVED was added in d9ca1c99 and accidentally removed as part of
ffe0e7cf when the high-resolution scrolling code was removed.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>