qcacld-3.0: Cleanup scan queue during driver unload

The following assert was observed during driver unload:
  QDF ASSERT in qdf_list_destroy Line 90
  PC is at hdd_scan_context_destroy+0x4c/0x78 [wlan]

There was also an associated memory leak detected:
 memory Leak@ File core/hdd/src/wlan_hdd_scan.c, @Line 562, size 48
 memory Leak@ File core/hdd/src/wlan_hdd_scan.c, @Line 2284, size 584

The issue is that the scan cleanup routine, hdd_cleanup_scan_queue(),
is currently only called during SSR and is not being called during the
driver unload sequence. Update the unload sequence to call this API.

Change-Id: Ib398a528cbb504bc132d985a0fa8c2a772d44332
CRs-Fixed: 2018045

core/hdd/src/wlan_hdd_main.c

@@ -5186,6 +5186,7 @@ static void hdd_wlan_exit(hdd_context_t *hdd_ctx)
 		 * the expectation is that by the time Request Full Power has
 		 * completed, all scans will be cancelled
 		 */
+		hdd_cleanup_scan_queue(hdd_ctx);
 		hdd_abort_mac_scan_all_adapters(hdd_ctx);
 		hdd_abort_sched_scan_all_adapters(hdd_ctx);
 		hdd_stop_all_adapters(hdd_ctx);