evdev: init pointer accel filters when we have rel x/y axes

evdev: init pointer accel filters when we have rel x/y axes

Some devices provide abs x/y and rel x/y. We can't know which event the device
will send. The Microsoft Surface Type Cover sends relative events, which
then crashes libinput when we don't have an accel filter set up.

So instead of checking that the device doesn't have ABS_X/Y, check for the
device to have REL_X/Y instead.

https://bugzilla.redhat.com/show_bug.cgi?id=1206869

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>