wacom: Support the WSTYLUS_3D stylus type

Wacom's new "Pro Pen 3D" stylus is declared as a new stylus type within
libwacom: WSTYLUS_3D. Now that the Wacom panel supports arbitrary three-
button styli, we can add specific support for this new stylus type to
suppress the warning message that is generated.

https://bugzilla.gnome.org/show_bug.cgi?id=790028