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>
diff --git a/drivers/net/wireless/mwifiex/cfg80211.c b/drivers/net/wireless/mwifiex/cfg80211.c
index df30107..c9bc5f5 100644
--- a/drivers/net/wireless/mwifiex/cfg80211.c
+++ b/drivers/net/wireless/mwifiex/cfg80211.c
@@ -2350,9 +2350,12 @@
 		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;