wil6210: multiple VIFs support for FTM

Added support for multiple VIFs to FTM and AOA measurements.
Each VIF has an independent FTM/AOA session. In theory they
can run concurrently but currently FW queues session requests
and executes them serially.

Change-Id: If44446678c703793e26fd2fb7c22b92652d3bb33
Signed-off-by: Lior David <liord@codeaurora.org>
Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>