staging: vt6656: [BUG] iwctl_siwencodeext return if device not open

Don't allow entry to iwctl_siwencodeext if device not open.

This fixes a race condition where wpa supplicant/network manager
enters the function when the device is already closed.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Cc: stable@vger.kernel.org # 3.8+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vt6656/iwctl.c

@@ -1634,6 +1634,9 @@ int iwctl_siwencodeext(struct net_device *dev, struct iw_request_info *info,
 	if (pMgmt == NULL)
 		return -EFAULT;
 
+	if (!(pDevice->flags & DEVICE_FLAGS_OPENED))
+		return -ENODEV;
+
 	buf = kzalloc(sizeof(struct viawget_wpa_param), GFP_KERNEL);
 	if (buf == NULL)
 		return -ENOMEM;