dm: core: Add a livetree function to check node status

Add a way to find out if a node is enabled or not, based on its 'status'
property.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/core/ofnode.c b/drivers/core/ofnode.c
index a68076b..8707209 100644
--- a/drivers/core/ofnode.c
+++ b/drivers/core/ofnode.c
@@ -226,6 +226,16 @@
 	}
 }
 
+bool ofnode_is_enabled(ofnode node)
+{
+	if (ofnode_is_np(node)) {
+		return of_device_is_available(ofnode_to_np(node));
+	} else {
+		return fdtdec_get_is_enabled(gd->fdt_blob,
+					     ofnode_to_offset(node));
+	}
+}
+
 ofnode ofnode_first_subnode(ofnode node)
 {
 	assert(ofnode_valid(node));