staging: ft1000-usb: remove unnecessary return statement

This fixes the following checkpatch.pl warning:
WARNING: void function return statements are not generally useful
Signed-off-by: Catalina Mocanu <catalina.mocanu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ft1000/ft1000-usb/ft1000_usb.c

@@ -246,8 +246,6 @@ static void ft1000_disconnect(struct usb_interface *interface)
 		kfree(ft1000dev);
 	}
 	kfree(pFileStart);
-
-	return;
 }
 
 static struct usb_driver ft1000_usb_driver = {