mei: prevent unloading mei hw modules while the device is opened.

chrdev_open() increases reference counter on cdev->owner. Instead of
assigning the owner to mei subsystem, the owner has to be set to the
underlaying HW module (mei_me or mei_txe), so once the device is opened
the HW module cannot be unloaded.

Cc: <stable@vger.kernel.org> #3.17+
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>