mei: bus: unregister callbacks upon me client disable call

Stop and unregister receive and notification callbacks
from the disable function, to allow its later re-enablement.

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