firmware: arm_scmi: Skip protocol initialisation for additional devices

The scmi bus now supports adding multiple devices per protocol,
and since scmi_protocol_init is called for each scmi device created,
we must avoid allocating protocol private data and initialising the
protocol itself if it is already initialised.

In order to achieve the same, we can simple replace the idr pointer
from protocol initialisation function to a dummy function.
Suggested-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/bus.c

@@ -60,6 +60,11 @@ static int scmi_protocol_init(int protocol_id, struct scmi_handle *handle)
 	return fn(handle);
 }
 
+static int scmi_protocol_dummy_init(struct scmi_handle *handle)
+{
+	return 0;
+}
+
 static int scmi_dev_probe(struct device *dev)
 {
 	struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
@@ -78,6 +83,10 @@ static int scmi_dev_probe(struct device *dev)
 	if (ret)
 		return ret;
 
+	/* Skip protocol initialisation for additional devices */
+	idr_replace(&scmi_protocols, &scmi_protocol_dummy_init,
+		    scmi_dev->protocol_id);
+
 	return scmi_drv->probe(scmi_dev);
 }