wlan: constify MAC address in cfg80211 for 3.18 support

The following cfg80211 interfaces constify the MAC addr params.
So make the corresonding changes to adapt the  new interface.

.add_station
.change_station
.del_station
.get_station

Change-Id: I09c64a33039db6bd7c3c72afd1d30486ea03d142
CRs-fixed: 882885
diff --git a/CORE/HDD/inc/wlan_hdd_cfg80211.h b/CORE/HDD/inc/wlan_hdd_cfg80211.h
index b1774bc..93e0931 100644
--- a/CORE/HDD/inc/wlan_hdd_cfg80211.h
+++ b/CORE/HDD/inc/wlan_hdd_cfg80211.h
@@ -969,6 +969,13 @@
 void* wlan_hdd_change_country_code_cb(void *pAdapter);
 void hdd_select_cbmode( hdd_adapter_t *pAdapter,v_U8_t operationChannel);
 
+v_U8_t* wlan_hdd_cfg80211_get_ie_ptr(
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,18,0))
+                                     const v_U8_t *pIes,
+#else
+                                     v_U8_t *pIes,
+#endif
+                                     int length, v_U8_t eid);
 
 #ifdef FEATURE_WLAN_CH_AVOID
 int wlan_hdd_send_avoid_freq_event(hdd_context_t *pHddCtx,