wlan: Compilation error for kernel version earlier than 3.18

There is a compilation error in api wlan_hdd_send_avoid_freq_event,
when cfg80211_vendor_event_alloc is used for kernel version earlier
than 3.18

To address this add a kernel version check in api
cfg80211_vendor_event_alloc call.

Change-Id: I8bc96f1988bc2d790d5ada4b3158cf4594f547e6
CRs-Fixed: 2222400
diff --git a/CORE/HDD/src/wlan_hdd_cfg80211.c b/CORE/HDD/src/wlan_hdd_cfg80211.c
index e92b5b7..74ce9f5 100644
--- a/CORE/HDD/src/wlan_hdd_cfg80211.c
+++ b/CORE/HDD/src/wlan_hdd_cfg80211.c
@@ -12812,7 +12812,11 @@
 
 	vendor_event =
 		cfg80211_vendor_event_alloc(
-			hdd_ctx->wiphy, &adapter->wdev, sizeof(sta_flags) +
+			hdd_ctx->wiphy,
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 18, 0))
+			&adapter->wdev,
+#endif
+			sizeof(sta_flags) +
 			VOS_MAC_ADDR_SIZE + NLMSG_HDRLEN,
 			QCA_NL80211_VENDOR_SUBCMD_LINK_PROPERTIES_INDEX,
 			GFP_KERNEL);