clk: add clk_set_parent()

Clocks may support multiple parents: this change introduces an
optional operation on the clk-uclass to set a clock's parent.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: David Wu <david.wu@rock-chips.com>

Series-changes: 2
- Fixed David's email address.

drivers/clk/clk-uclass.c

@@ -188,6 +188,18 @@ ulong clk_set_rate(struct clk *clk, ulong rate)
 	return ops->set_rate(clk, rate);
 }
 
+int clk_set_parent(struct clk *clk, struct clk *parent)
+{
+	const struct clk_ops *ops = clk_dev_ops(clk->dev);
+
+	debug("%s(clk=%p, parent=%p)\n", __func__, clk, parent);
+
+	if (!ops->set_parent)
+		return -ENOSYS;
+
+	return ops->set_parent(clk, parent);
+}
+
 int clk_enable(struct clk *clk)
 {
 	const struct clk_ops *ops = clk_dev_ops(clk->dev);