of: Properly set the OF_POPULATED_BUS flag on root node

of_platform_populate() takes a subset of the device tree and turns it
into a set of platform_devices. At the same time it sets the
OF_POPULATED_BUS flag in each bus nodes so that of_platform_depopulate()
can undo the operation at a later time. However, it doesn't set the flag
on the root of the population tree which means that dynamic modifications
of the device tree at runtime will not create/destroy devices correctly.

Fix of_platform_populate() to set the OF_POPULATED_BUS flag on the node
it is called with.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Cc: Pawel Moll <pawel.moll@arm.com>

drivers/of/platform.c

@@ -500,6 +500,7 @@ int of_platform_populate(struct device_node *root,
 		if (rc)
 			break;
 	}
+	of_node_set_flag(root, OF_POPULATED_BUS);
 
 	of_node_put(root);
 	return rc;
@@ -542,7 +543,10 @@ static int of_platform_device_destroy(struct device *dev, void *data)
  */
 void of_platform_depopulate(struct device *parent)
 {
-	device_for_each_child(parent, NULL, of_platform_device_destroy);
+	if (parent->of_node && of_node_check_flag(parent->of_node, OF_POPULATED_BUS)) {
+		device_for_each_child(parent, NULL, of_platform_device_destroy);
+		of_node_clear_flag(parent->of_node, OF_POPULATED_BUS);
+	}
 }
 EXPORT_SYMBOL_GPL(of_platform_depopulate);