evdev: Prefer pointer/touch devices over keyboard devices

In keyboard/mouse wireless combos, it is rather common for the mouse to
claim it contains the multimedia keys, this makes libinput enable both
the pointer and keyboard capabilities on this device, and Clutter thus
to create a keyboard ClutterInputDevice for it.

Ideally clutter devices should be able to reflect their full capabilities,
or maybe account for the fact that certain events can be sent from
seemingly unexpected device types. But this will bring a somewhat better
behavior on such devices.

https://bugzilla.gnome.org/show_bug.cgi?id=740518