ubuntu: Add USB tablet device support

As reported by Cole Robinson, none of the ubuntu distro metadata reports
support for the USB tablet device.

After testing old Ubuntu ISOs, seems that 5.04 is the first bootable one
that supports it (4.10, the first one, wasn't bootable though).

Resolves: rhbz#1423024

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Acked-by: Christophe Fergeau <cfergeau@redhat.com>