qcacld-3.0: Refine the extscan stop scan logic

Make the following updates to the extscan stop scan 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: Ie4a693b4a91d728a075cffad3ee368b22d9c5b2a
CRs-Fixed: 2335647
7 files changed