dm: core: Use dev_has_ofnode() instead of dev_of_valid()

We have two functions which do the same thing. Standardise on
dev_has_ofnode() since there is no such thing as an 'invalid' ofnode in
normal operation: it is either null or missing.

Also move the functions into one place.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c
index ac954a3..5cfd00c 100644
--- a/drivers/clk/clk-uclass.c
+++ b/drivers/clk/clk-uclass.c
@@ -345,7 +345,7 @@
 {
 	int ret;
 
-	if (!dev_of_valid(dev))
+	if (!dev_has_ofnode(dev))
 		return 0;
 
 	/* If this not in SPL and pre-reloc state, don't take any action. */