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/arch/arm/mach-rockchip/rk3399/sdram_rk3399.c b/arch/arm/mach-rockchip/rk3399/sdram_rk3399.c
index 536879d..a3ae8bd 100644
--- a/arch/arm/mach-rockchip/rk3399/sdram_rk3399.c
+++ b/arch/arm/mach-rockchip/rk3399/sdram_rk3399.c
@@ -1128,7 +1128,7 @@
 #if !CONFIG_IS_ENABLED(OF_PLATDATA)
 	struct rockchip_dmc_plat *plat = dev_get_platdata(dev);
 	const void *blob = gd->fdt_blob;
-	int node = dev->of_offset;
+	int node = dev_of_offset(dev);
 	int ret;
 
 	ret = fdtdec_get_int_array(blob, node, "rockchip,sdram-params",