mei: mei_me_client is not hw API move to mei_dev.h

Move struct mei_me_client from hw.h to mei_dev.h as it is not
part of the hardware API. The structutre doesn't have to
be packed. Add kdoc for this structure.

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