greybus: update descriptor module_id->module to match spec

Greybus spec was updated to change the name of the Module ID descriptor
to simply Module descriptor. Change everything accordingly.

Signed-off-by: Matt Porter <mporter@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>