During the roam scan, if there are no desired APs found in the partial
frequency list, an immediate full scan on all the supported frequencies
is initiated as a fallback. This would include the 6 GHz PSC
frequencies by default.
This attribute allow that behavior to be modified to include PSCs only
if 6 GHz use has been detected in the environment.
Change-Id: I6dc380419f14b920737fd87cd9a487c28364563b
CRs-Fixed: 3351697