dm: core: Replace of_offset with accessor

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/exynos/pinctrl-exynos.c b/drivers/pinctrl/exynos/pinctrl-exynos.c
index dd0a16e..5b9a592 100644
--- a/drivers/pinctrl/exynos/pinctrl-exynos.c
+++ b/drivers/pinctrl/exynos/pinctrl-exynos.c
@@ -70,7 +70,7 @@
 int exynos_pinctrl_set_state(struct udevice *dev, struct udevice *config)
 {
 	const void *fdt = gd->fdt_blob;
-	int node = config->of_offset;
+	int node = dev_of_offset(config);
 	unsigned int count, idx, pin_num;
 	unsigned int pinfunc, pinpud, pindrv;
 	unsigned long reg, value;