libfdt: Add fdt_overlay_apply to the exported symbols

fdt_overlay_apply was not usable in the shared library. Export it to allow
its use.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/libfdt/version.lds b/libfdt/version.lds
index 1f4e1ea..cff0358 100644
--- a/libfdt/version.lds
+++ b/libfdt/version.lds
@@ -61,6 +61,7 @@
 		fdt_size_cells;
 		fdt_stringlist_contains;
 		fdt_resize;
+		fdt_overlay_apply;
 
 	local:
 		*;