qcacld-3.0: Remove survey_idx field from struct hdd_adapter

Change I2fa509f53b47d65ba0f4abbc438834b85b9c21f6 ("qcacld-3.0: Report
more information in survey dump") removed the legacy survey code that
utilized the survey_idx field in struct hdd_adapter. Since the field
is now obsolete, remove it.

Change-Id: I59653739949692eee4c15d5db1db386deb2d4182
CRs-Fixed: 2368707

core/hdd/inc/wlan_hdd_main.h

@@ -1331,8 +1331,6 @@ struct hdd_adapter {
 	struct hdd_multicast_addr_list mc_addr_list;
 	uint8_t addr_filter_pattern;
 
-	bool survey_idx;
-
 	struct hdd_scan_info scan_info;
 
 	/* Flag to ensure PSB is configured through framework */