HID: wacom: generic: add support for touchring

Add support for the touchring to the generic code path in support of the second
generation Intuos Pro.

We also add checks for usage->type to ensure that we handle the usage before we
report it, or change the inrange_state based on it.

Signed-off-by: Aaron Skomra <aaron.skomra@wacom.com>
Reviewed-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>