greybus: tracing: fix host device num_cports

The type of the gb_host_device num_cports field is size_t.  Correct
the num_cports data recorded with a host device event so its type
matches that; fix the format length modifier used for it as well.

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