HID: wacom: Set default device name to value from wacom->features

Allocated input devices should not use the 'pen_name' by default since
we do not know at that point in time if that is an appropriate choice
of name. Instead, use the (tool-agnostic) name that is stored in the
device's 'wacom_features' structure. This also has the nice side-effect
of requring us to be explicit about the naming of the pen device, as
we already are for touch and pad devices.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>