fdt: Add a function to look up a /chosen property

It is sometimes useful to find a property in the chosen node. Add a function
for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index 9db033a..e1df144 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -601,16 +601,21 @@
 	return -ENOENT;
 }
 
+const char *fdtdec_get_chosen_prop(const void *blob, const char *name)
+{
+	int chosen_node;
+
+	if (!blob)
+		return NULL;
+	chosen_node = fdt_path_offset(blob, "/chosen");
+	return fdt_getprop(blob, chosen_node, name, NULL);
+}
+
 int fdtdec_get_chosen_node(const void *blob, const char *name)
 {
 	const char *prop;
-	int chosen_node;
-	int len;
 
-	if (!blob)
-		return -FDT_ERR_NOTFOUND;
-	chosen_node = fdt_path_offset(blob, "/chosen");
-	prop = fdt_getprop(blob, chosen_node, name, &len);
+	prop = fdtdec_get_chosen_prop(blob, name);
 	if (!prop)
 		return -FDT_ERR_NOTFOUND;
 	return fdt_path_offset(blob, prop);