coresight: delay initialisation when children are missing

Depending on when CoreSight device are discovered it is possible
that some IP block may be referencing devices that have not been
added to the bus yet.  The end result is missing nodes in the
CoreSight topology even when the devices are present and properly
initialised.

This patch solves the problem by asking the driver core to
try initialising the device at a later time when the children
of a CoreSight node are missing.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/of_coresight.c

@@ -166,7 +166,7 @@ struct coresight_platform_data *of_get_coresight_platform_data(
 
 			rdev = of_coresight_get_endpoint_device(rparent);
 			if (!rdev)
-				continue;
+				return ERR_PTR(-EPROBE_DEFER);
 
 			pdata->child_names[i] = dev_name(rdev);
 			pdata->child_ports[i] = rendpoint.id;