qcacld-3.0: Decouple get channel command from extscan

Currently get valid channel vandor command is defined
under EXTSCAN feature and also depends on gExtScanEnable
ini. when Extscan feature is disabled by ini or by feature
flag this command doesn't work.

As this command is to get the valid channel list, this
should not depend on extscan feature.

To address above issue, decouple get valid channel command
from extscan feature.

Change-Id: I6496cb94e6330f071f8027607e7d55a8f5d3db8a
CRs-Fixed: 2518313
7 files changed