mei: bus: add module_mei_cl_driver helper macro

Add module_mei_cl_driver helper macro for eliminating the boilerplate
code from mei_cl drivers registration. The macro is intended for
drivers which in their init/exit sections does only register/unregister
of a mei_cl driver.

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