qcacld-3.0: Remove PowerUsageControl from struct hdd_config
As part of change Iac183da52495aca07c6270edeb9f383ab49c1ff5
("qcacld-3.0: Add CFG items of power") support for the INI item
"gPowerUsage" was moved from HDD to MLME. However that change left
behind the PowerUsageControl field in struct hdd_config. This is now
obsolete, so remove it.
Change-Id: If5eb74b91f79288a2431b0e806ad89cd3d41b503
CRs-Fixed: 2368702