dm: core: Allow uclass to set up a device's child after it is probed

Some buses need to set up their child devices after they are probed.
Support a common child_post_probe() method for the uclass.

With this change, the two APIs uclass_pre_probe_device() and
uclass_post_probe_device() become symmetric.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c
index 3113d6a..3c7b9cf 100644
--- a/drivers/core/uclass.c
+++ b/drivers/core/uclass.c
@@ -687,8 +687,19 @@
 
 int uclass_post_probe_device(struct udevice *dev)
 {
-	struct uclass_driver *uc_drv = dev->uclass->uc_drv;
+	struct uclass_driver *uc_drv;
+	int ret;
+
+	if (dev->parent) {
+		uc_drv = dev->parent->uclass->uc_drv;
+		if (uc_drv->child_post_probe) {
+			ret = uc_drv->child_post_probe(dev);
+			if (ret)
+				return ret;
+		}
+	}
 
+	uc_drv = dev->uclass->uc_drv;
 	if (uc_drv->post_probe)
 		return uc_drv->post_probe(dev);