dm: core: Replace of_offset with accessor (part 2)

At present devices use a simple integer offset to record the device tree
node associated with the device. In preparation for supporting a live
device tree, which uses a node pointer instead, refactor existing code to
access this field through an inline function.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pinctrl/pinctrl_stm32.c b/drivers/pinctrl/pinctrl_stm32.c
index d7b5ea3..5bee7fb 100644
--- a/drivers/pinctrl/pinctrl_stm32.c
+++ b/drivers/pinctrl/pinctrl_stm32.c
@@ -101,7 +101,7 @@
 	int rv, len;
 
 	/* Get node pinctrl-0 */
-	rv = fdtdec_parse_phandle_with_args(gd->fdt_blob, periph->of_offset,
+	rv = fdtdec_parse_phandle_with_args(gd->fdt_blob, dev_of_offset(periph),
 					   "pinctrl-0", 0, 0, 0, &args);
 	if (rv)
 		return rv;