mei: add pci driver ops shutdown handler.

The shutdown handler quiesces the device, it performs link reset in
order to close all connections and notify the device that is not longer
managed by the driver.
This is essentially a stripped down version of the PCI remove() function
where only the necessary amount of work is done to stop any further
activity.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>