clk: clk_set_default: accept no-op skip fields

The Assigned Clock parents and rates misses the fact that a "0" entry can
be passed to skip setting a parent or rate of an assigned clock as
described in the Linux clock bindings at [1].

This patch simply skips the clock reparenting if the DT parsing returns
-ENOENT and the clock rate setting if "0" is passed as clock rate.

[1] https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/clock/clock-bindings.txt#L135

Fixes: f4fcba5c5b "clk: implement clk_set_defaults()"
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/clk/clk-uclass.c

@@ -154,6 +154,10 @@ static int clk_set_default_parents(struct udevice *dev)
 	for (index = 0; index < num_parents; index++) {
 		ret = clk_get_by_indexed_prop(dev, "assigned-clock-parents",
 					      index, &parent_clk);
+		/* If -ENOENT, this is a no-op entry */
+		if (ret == -ENOENT)
+			continue;
+
 		if (ret) {
 			debug("%s: could not get parent clock %d for %s\n",
 			      __func__, index, dev_read_name(dev));
@@ -210,6 +214,10 @@ static int clk_set_default_rates(struct udevice *dev)
 		goto fail;
 
 	for (index = 0; index < num_rates; index++) {
+		/* If 0 is passed, this is a no-op */
+		if (!rates[index])
+			continue;
+
 		ret = clk_get_by_indexed_prop(dev, "assigned-clocks",
 					      index, &clk);
 		if (ret) {