Fix: sink.text.details: goto error when failing to add input port

If bt_self_component_sink_add_input_port fails, the current code does
not goto error.  This patch fixes it.  It also changes the switch, used
to convert from `add_port_status` to `status`, to a cast, as is the
practice throughout the project.

Change-Id: I82b2719316ad00ffd9d9c14b86b8890b98130669
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/3383
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>