USB: option: fix memory leak

Fix memory leak introduced by commit 383cedc3bb435de7a2 ("USB: serial:
full autosuspend support for the option driver") which allocates
usb-serial data but never frees it.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/option.c

@@ -47,6 +47,7 @@
 /* Function prototypes */
 static int  option_probe(struct usb_serial *serial,
 			const struct usb_device_id *id);
+static void option_release(struct usb_serial *serial);
 static int option_send_setup(struct usb_serial_port *port);
 static void option_instat_callback(struct urb *urb);
 
@@ -1251,7 +1252,7 @@ static struct usb_serial_driver option_1port_device = {
 	.ioctl             = usb_wwan_ioctl,
 	.attach            = usb_wwan_startup,
 	.disconnect        = usb_wwan_disconnect,
-	.release           = usb_wwan_release,
+	.release           = option_release,
 	.read_int_callback = option_instat_callback,
 #ifdef CONFIG_PM
 	.suspend           = usb_wwan_suspend,
@@ -1333,6 +1334,15 @@ static int option_probe(struct usb_serial *serial,
 	return 0;
 }
 
+static void option_release(struct usb_serial *serial)
+{
+	struct usb_wwan_intf_private *priv = usb_get_serial_data(serial);
+
+	usb_wwan_release(serial);
+
+	kfree(priv);
+}
+
 static void option_instat_callback(struct urb *urb)
 {
 	int err;