Align wigig tethering changes with upstream

The current code-base contain tethering support for
wigig framework. Recently a simplified change was
ported from upstream. Align the code to be consistent
with the upstream change:
- TETHERING_WIGIG is internal type, not public
- Remove usage of system properties

Change-Id: I171f2687fe3cafddcf7d39cd46ca7d060b52e747
CRs-Fixed: 2713745
9 files changed