wil6210: support FTM/AOA while unassociated

Prepare driver for FTM/AOA while unassociated.
1. Added attributes allowing user space to specify the frequency
where FTM/AOA peer is listening. When specified it will override
the entry in the kernel scan results cache. If not specified,
the kernel scan results cache will be used like today.
This gives user space location framework more flexibility - it
can maintain its own cache of peers, or perform scans less
often (since entries in the kernel scan results cache expire
quickly)
2. Remove associated check when starting FTM session, so session
can start even when unassociated.

Change-Id: Ib0ba52c506e1d8d59ab8c12043acd792405d69a0
CRs-Fixed: 1094147
Signed-off-by: Lior David <liord@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>