dm: clk: Add support for of-platdata

Add support for this feature in the core clock code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/clk/clk_fixed_rate.c b/drivers/clk/clk_fixed_rate.c
index 797e537..9c4d2b3 100644
--- a/drivers/clk/clk_fixed_rate.c
+++ b/drivers/clk/clk_fixed_rate.c
@@ -30,9 +30,11 @@
 
 static int clk_fixed_rate_ofdata_to_platdata(struct udevice *dev)
 {
+#if !CONFIG_IS_ENABLED(OF_PLATDATA)
 	to_clk_fixed_rate(dev)->fixed_rate =
 				fdtdec_get_int(gd->fdt_blob, dev->of_offset,
 					       "clock-frequency", 0);
+#endif
 
 	return 0;
 }