HID: wacom: rename failN with some meaningful information

When we have to deal with new elements in probe, having the exit labels
named sequencially is a pain to maintain. Put a meaningful name instead
so that we do not have to renumber them on inserts.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Jason Gerecke <killertofu@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>