greybus: Move id-field before bundle-field in CPort Descriptor.

Note that this also makes sure the id-field is naturally aligned in case
we ever were to remove the __packed attribute.

Reviewed-by: Alex Elder <elder@linaro.org>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>