Add support for Waltop Slim Tablet 12.1 inch by fixing its report descriptor.
This mainly fixes button reporting.

This tablet is also sold as Genius G-Pen F610.
Other possible names of this tablet: VisTablet Original 12", Adesso CyberTablet
Z12, Adesso CT-Z12A, PenPower Tooya Pro, Aiptek Slim 12.1 Inch
Signed-off-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>