qcacld-3.0: Remove obsolete prevent_link_down from hdd cfg

After CFG INI componentization hdd prevent link down config
is obsolete and hence remove it from hdd config.

Change-Id: Ibcceef38b9aedfb323e859ff0c20d1b068dce08d
CRs-Fixed: 2397353

core/hdd/inc/wlan_hdd_cfg.h

@@ -173,7 +173,6 @@ struct hdd_config {
 #ifdef ENABLE_MTRACE_LOG
 	bool enable_mtrace;
 #endif
-	bool prevent_link_down;
 	bool fEnableSNRMonitoring;
 	bool advertiseConcurrentOperation;
 #ifdef DHCP_SERVER_OFFLOAD