mei: rename mei_cl_cb.information to mei_cl_cb.buf_idx

rename 'information' member of the struct mei_cl_cb to
more self-descriptive 'buf_idx'

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