qcacld-3.0: Add flag for increased Tx descs

Add flag for increased Tx descs. And Enable the flag for qca6490.
Based on 1Tx:8Rx NAN test case experiment, it requires increase in
Tx descriptors to burst trafficto each Rx device.

Change-Id: I364ada1ee80afcaf3db3d50efa16a95054a4f7f4
CRs-Fixed: 2658549
2 files changed