fdtdec: correct test on return of fdt_node_offset_by_phandle

The result of fdt_node_offset_by_phandle is negative for error,
so this patch corrects the check of this result in
fdtdec_parse_phandle_with_args.

This patch allows to have the same behavior with or without OF_LIVE
for the function dev_read_phandle_with_args with cell_name = NULL and
with invalid phandle.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index b8fc5e2..ee1bd41 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -746,7 +746,7 @@
 			if (cells_name || cur_index == index) {
 				node = fdt_node_offset_by_phandle(blob,
 								  phandle);
-				if (!node) {
+				if (node < 0) {
 					debug("%s: could not find phandle\n",
 					      fdt_get_name(blob, src_node,
 							   NULL));