qcacld-3.0: Refine the extscan get capabilities logic

Make the following updates to the extscan get capabilities logic:
1) Exclusively use the Unified WMI data structures.
2) Update the HDD<=>SME interface to enforce the contract that SME
   must not make any assumptions about the buffers provided by HDD.

Change-Id: I9e57c86a3da0924af01d82d626b61c28f7d520bf
CRs-Fixed: 2330211
7 files changed