Input: aiptek - use descriptors of current altsetting

Make sure to always use the descriptors of the current alternate setting
to avoid future issues when accessing fields that may differ between
settings.

Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Vladis Dronov <vdronov@redhat.com>
Link: https://lore.kernel.org/r/20191210113737.4016-4-johan@kernel.org


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>