HID: waltop: add support for Waltop Slim Tablet 12.1 inch

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>