HID: wacom: untie leds from inputs

Like remotes, LEDs should be handled by themself, not magically behind
the inputs as they have a complete different life.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>