dm: core: Add dev_get_uclass_priv() to access uclass private data

Add a convenience function to access the private data that a uclass stores
for each of its devices. Convert over most existing uses for consistency
and to provide an example for others.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/core/device.c b/drivers/core/device.c
index 73c3e07..92e8a57 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -305,6 +305,16 @@
 	return dev->priv;
 }
 
+void *dev_get_uclass_priv(struct udevice *dev)
+{
+	if (!dev) {
+		dm_warn("%s: null device\n", __func__);
+		return NULL;
+	}
+
+	return dev->uclass_priv;
+}
+
 void *dev_get_parentdata(struct udevice *dev)
 {
 	if (!dev) {