ZC0301 driver updates.

Changes: + new, - removed, * cleanup, @ bugfix

@ Need usb_get|put_dev() when disconnecting, if the device is open
* Cleanups and updates in the documentation
+ Use per-device sensor structures
+ Add frame_timeout module parameter
Signed-off-by: Luca Risolia <luca.risolia@studio.unibo.it>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>