Since 8769b3d55, the checks performed on which update_* function was
called for each device got quite more lax, leading to failed asserts
on code that assumed the previous behavior.
Change update_[mouse|touchpad|trackball]_* to bail out early if the
device received has not the right type, and remove the asserts.
https://bugzilla.gnome.org/show_bug.cgi?id=747886
8dfb88b669