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/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 7163fa2..0e4a4eb 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -244,7 +244,7 @@
 		return -EOPNOTSUPP;
 
 	for (i = 0; i < ofcfg->grpsz; i++) {
-		val[i] = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+		val[i] = fdtdec_get_uint(gd->fdt_blob, dev_of_offset(dev),
 					 ofcfg->grp[i].name, -1);
 		offset = ofcfg->grp[i].off;
 		if (val[i] == -1) {
diff --git a/drivers/net/phy/ti.c b/drivers/net/phy/ti.c
index c55dd97..d1ce406 100644
--- a/drivers/net/phy/ti.c
+++ b/drivers/net/phy/ti.c
@@ -167,13 +167,13 @@
 	struct dp83867_private *dp83867 = phydev->priv;
 	struct udevice *dev = phydev->dev;
 
-	dp83867->rx_id_delay = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+	dp83867->rx_id_delay = fdtdec_get_uint(gd->fdt_blob, dev_of_offset(dev),
 				 "ti,rx-internal-delay", -1);
 
-	dp83867->tx_id_delay = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+	dp83867->tx_id_delay = fdtdec_get_uint(gd->fdt_blob, dev_of_offset(dev),
 				 "ti,tx-internal-delay", -1);
 
-	dp83867->fifo_depth = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+	dp83867->fifo_depth = fdtdec_get_uint(gd->fdt_blob, dev_of_offset(dev),
 				 "ti,fifo-depth", -1);
 
 	return 0;
diff --git a/drivers/net/phy/xilinx_phy.c b/drivers/net/phy/xilinx_phy.c
index 920bfcb..3f80f04 100644
--- a/drivers/net/phy/xilinx_phy.c
+++ b/drivers/net/phy/xilinx_phy.c
@@ -104,7 +104,7 @@
 	u32 phytype;
 
 	debug("%s\n", __func__);
-	phytype = fdtdec_get_int(gd->fdt_blob, phydev->dev->of_offset,
+	phytype = fdtdec_get_int(gd->fdt_blob, dev_of_offset(phydev->dev),
 				 "phy-type", -1);
 	if (phytype == XAE_PHY_TYPE_1000BASE_X)
 		phydev->flags |= XAE_PHY_TYPE_1000BASE_X;