mwifiex: fix memory leak issue when driver unload

After unregister_netdevice() call the request is queued and
reg_state is changed to NETREG_UNREGISTERING.
As we check for NETREG_UNREGISTERED state, free_netdev() never
gets executed causing memory leak.

Initialize "dev->destructor" to free_netdev() to free device
data after unregistration.

Cc: <stable@vger.kernel.org>
Reported-by: Daniel Drake <dsd@laptop.org>
Tested-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.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/main.c b/drivers/net/wireless/mwifiex/main.c
index 121443a..2eb88ea 100644
--- a/drivers/net/wireless/mwifiex/main.c
+++ b/drivers/net/wireless/mwifiex/main.c
@@ -655,6 +655,7 @@
 						struct net_device *dev)
 {
 	dev->netdev_ops = &mwifiex_netdev_ops;
+	dev->destructor = free_netdev;
 	/* Initialize private structure */
 	priv->current_key_index = 0;
 	priv->media_connected = false;