Use Nyx Mass Storage Mode device instead of Nyx System device

- Increment version number to 2.2.0
- Update nyx-lib version requirement in README.md
- Use new Nyx Mass Storage Mode API

Open-webOS-DCO-1.0-Signed-off-by: Pekka Ropo <pekka.ropo@palm.com>

Change-Id: I92f5ce3d30053e45a6d46e32e6f027053ddc505e
Reviewed-on: http://g2g.palm.com/1220
Reviewed-by: Build Verification
Tested-by: Pekka Ropo <pekka.ropo@palm.com>
Reviewed-by: Keith Derrick <keith.derrick@palm.com>