clk: imx: imx8mm: add set_parent callback

Add set_parent callback, then assigned-clock-parents in dts could
be work.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
diff --git a/drivers/clk/imx/clk-imx8mm.c b/drivers/clk/imx/clk-imx8mm.c
index 4911345..091b092 100644
--- a/drivers/clk/imx/clk-imx8mm.c
+++ b/drivers/clk/imx/clk-imx8mm.c
@@ -175,11 +175,30 @@
 	return __imx8mm_clk_enable(clk, 1);
 }
 
+static int imx8mm_clk_set_parent(struct clk *clk, struct clk *parent)
+{
+	struct clk *c, *cp;
+	int ret;
+
+	debug("%s(#%lu), parent: %lu\n", __func__, clk->id, parent->id);
+
+	ret = clk_get_by_id(clk->id, &c);
+	if (ret)
+		return ret;
+
+	ret = clk_get_by_id(parent->id, &cp);
+	if (ret)
+		return ret;
+
+	return clk_set_parent(c, cp);
+}
+
 static struct clk_ops imx8mm_clk_ops = {
 	.set_rate = imx8mm_clk_set_rate,
 	.get_rate = imx8mm_clk_get_rate,
 	.enable = imx8mm_clk_enable,
 	.disable = imx8mm_clk_disable,
+	.set_parent = imx8mm_clk_set_parent,
 };
 
 static int imx8mm_clk_probe(struct udevice *dev)