HID Device role API fixes

This change reflects the API update, and also fixes a couple
issues with the code (non-initialized, wrongly compared and
otherwise unused mHidDevice field).

It keeps the current logic of using a single device at a time,
yet introduces checks that the application is actually
addressing the right device.

Test: make
Change-Id: I088417046907c8310692cf9205075d6da0cd81e6