Don't sync the MT state for fake MT devices

Don't sync the MT state for fake MT devices

Devices with ABS_MT_SLOT-1 are fake MT devices, they merely overlap the
axis range but don't actually provide slots. The EVIOCGABS ioctl won't work to
retrieve the current value - the kernel does not store values for those axes
and the return value is always 0.

Thus, simply ignore those axes for fake MT devices and instead rely on the
next event to update the caller with the correct state for each axis.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>