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/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c
index 456cf3b..be56785 100644
--- a/drivers/i2c/i2c-uclass.c
+++ b/drivers/i2c/i2c-uclass.c
@@ -678,7 +678,7 @@
 #if CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)
 	struct dm_i2c_chip *plat = dev_get_parent_plat(dev);
 
-	if (!dev_of_valid(dev))
+	if (!dev_has_ofnode(dev))
 		return 0;
 	return i2c_chip_of_to_plat(dev, plat);
 #else