qcacld-3.0: Enable flag for increased Tx descs in QCA6390
Enable the increased tx descriptors flag for qca6390.
Based on 1Tx:8Rx NAN test case experiment, it requires
increase in Tx descriptors to burst trafficto each Rx device.
Change-Id: I7978732fda7149bf4c6ffaf4ea29f4e5dd30fd95
CRs-Fixed: 2665503