HID: waltop: fix Media Tablet 10.6 inch scrolling

Add support for horizontal scrolling with Waltop Media Tablet 10.6 inch by
updating the fixed HID report descriptor.

The horizontal/vertical scrolling is toggled by pressing the wheels' center
buttons while in scroll mode, which wasn't discovered at the time the
support for this tablet was added.

Signed-off-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>