HID: hid-belkin: clean up usage of 'driver_data'

HID: hid-belkin: clean up usage of 'driver_data'

The module is storing an integer inside the drvdata pointer, which is
confusing, lets fix this and set the whole of 'hid_device_id' struct
as the drvdata and then simply use its integer 'driver_data' field for
quirks, which shall make the code cleaner, type-safe, consistent and
more readable.

This makes the cast to (void *) during storage a bit safer (just to
suppress the const qualifier warning) and the cast to (unsigned long)
during retrieval is removed.

Signed-off-by: Pawel Zalewski (The Capable Hub) <pzalewski@thegoodpenguin.co.uk>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>