qcacld-3.0: Stop SAP if all channels are disabled

User disables all the channels when the SAP is in
operation, and policy manager restart sap functionality
cannot get any valid channels and SAP also doesn't stop.
Later, kernel stops the SAP, since it is operating on an
invalid channel.

To fix this, restart the SAP on a valid channel only if
atleast one valid channel is available. Otherwise, stop
the SAP instead of waiting for kernel to stop the SAP.

CRs-Fixed: 3617706
Change-Id: Ia613b8e9585ff19aae9bf97ea5d0fc230ae41c5f