mei: bus: Add device enabling and disabling API

It should be left to the drivers to enable and disable the device on the
MEI bus when e.g getting probed.
For drivers to be able to safely call the enable and disable hooks, the
mei_cl_ops must be set before it's probed and thus this should happen
before registering the device on the MEI bus. Hence the mei_cl_add_device()
prototype change.

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