mwifiex: fix potential null dereference 'mef_entry'

drivers/net/wireless/mwifiex/cfg80211.c:2357 mwifiex_cfg80211_suspend()
  error: potential null dereference 'mef_entry'
  (kzalloc returns null)
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mwifiex/cfg80211.c

@@ -2350,9 +2350,12 @@ static int mwifiex_cfg80211_suspend(struct wiphy *wiphy,
 		return 0;
 	}
 
+	mef_entry = kzalloc(sizeof(*mef_entry), GFP_KERNEL);
+	if (!mef_entry)
+		return -ENOMEM;
+
 	memset(&mef_cfg, 0, sizeof(mef_cfg));
 	mef_cfg.num_entries = 1;
-	mef_entry = kzalloc(sizeof(*mef_entry), GFP_KERNEL);
 	mef_cfg.mef_entry = mef_entry;
 	mef_entry->mode = MEF_MODE_HOST_SLEEP;
 	mef_entry->action = MEF_ACTION_ALLOW_AND_WAKEUP_HOST;