libfdt: add missing version symbols

These symbols were not added to the version script when they were added
to libfdt.

Signed-off-by: Brandon Maier <brandon.maier@collins.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/version.lds

@@ -78,6 +78,8 @@ LIBFDT_1.2 {
 		fdt_setprop_inplace_namelen_partial;
 		fdt_create_with_flags;
 		fdt_overlay_target_offset;
+		fdt_get_symbol;
+		fdt_get_symbol_namelen;
 	local:
 		*;
 };