wlan: Don't decrease no of sessions if no of session is zero.

If due to some reason wlan_hdd_decr_active_session
is being called when active sessions are zero;
wlan_hdd_decr_active_session will make active sessions
as 255. Next time driver will not be able to connect
as no of connected sessions will be 255.
Fix is to Don't decrease no of sessions if no of session is
zero.

CRs-Fixed: 704947
Change-Id: I29b5112b042b84872d243b53ba5b912e4823a41f
diff --git a/CORE/HDD/src/wlan_hdd_main.c b/CORE/HDD/src/wlan_hdd_main.c
index 3aab209..5dd9352 100644
--- a/CORE/HDD/src/wlan_hdd_main.c
+++ b/CORE/HDD/src/wlan_hdd_main.c
@@ -9942,7 +9942,11 @@
    case VOS_P2P_CLIENT_MODE:
    case VOS_P2P_GO_MODE:
    case VOS_STA_SAP_MODE:
-        pHddCtx->no_of_active_sessions[mode]--;
+        if (pHddCtx->no_of_active_sessions[mode] > 0)
+            pHddCtx->no_of_active_sessions[mode]--;
+        else
+            hddLog(VOS_TRACE_LEVEL_INFO, FL(" No.# of Active sessions"
+                                     "is already Zero"));
         break;
    default:
         hddLog(VOS_TRACE_LEVEL_INFO, FL("Not Expected Mode %d"), mode);