dm: core: Add a function to get a device's uclass ID

This is useful to check which uclass a device is in.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

drivers/core/device.c

@@ -438,3 +438,8 @@ ulong dev_get_of_data(struct udevice *dev)
 {
 	return dev->of_id->data;
 }
+
+enum uclass_id device_get_uclass_id(struct udevice *dev)
+{
+	return dev->uclass->uc_drv->id;
+}