pinctrl: exit pinconfig_post_bind if there are no subnodes

This fixes RK3288 SPL hanging or hitting this assert:
drivers/core/ofnode.c:183: ofnode_first_subnode: Assertion `ofnode_valid(node)' failed.

Signed-off-by: Urja Rannikko <urjaman@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/drivers/pinctrl/pinctrl-uclass.c b/drivers/pinctrl/pinctrl-uclass.c
index 0e6c559..f01bc77 100644
--- a/drivers/pinctrl/pinctrl-uclass.c
+++ b/drivers/pinctrl/pinctrl-uclass.c
@@ -116,6 +116,9 @@
 	ofnode node;
 	int ret;
 
+	if (!dev_of_valid(dev))
+		return 0;
+
 	dev_for_each_subnode(node, dev) {
 		if (pre_reloc_only &&
 		    !ofnode_pre_reloc(node))