qcacld-3.0: Fix ASSERT while loading driver

Currently in csr_purge_old_scan_results() mutex_lock
did't acquire by current thread but same thread is
releasing the lock due to which there is a ASSERT while
releasing mutex_lock.

Fix is to acuire the mutex_lock properly before releasing.

Change-Id: I1023dca73ffaa3d3b3a123d474c3ac5b0e1c1af2
CRs-Fixed: 2020452

core/sme/src/csr/csr_api_scan.c

@@ -3060,7 +3060,7 @@ static void csr_purge_old_scan_results(tpAniSirGlobal mac_ctx)
 	uint64_t oldest_entry = 0;
 	uint64_t curr_time = (uint64_t)qdf_mc_timer_get_system_time();
 
-	csr_ll_unlock(&mac_ctx->scan.scanResultList);
+	csr_ll_lock(&mac_ctx->scan.scanResultList);
 	pentry = csr_ll_peek_head(&mac_ctx->scan.scanResultList,
 					LL_ACCESS_NOLOCK);
 	while (pentry) {