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/mmc/socfpga_dw_mmc.c b/drivers/mmc/socfpga_dw_mmc.c
index 0a22e58..d0c3c51 100644
--- a/drivers/mmc/socfpga_dw_mmc.c
+++ b/drivers/mmc/socfpga_dw_mmc.c
@@ -70,7 +70,7 @@
 		return -EINVAL;
 	}
 
-	fifo_depth = fdtdec_get_int(gd->fdt_blob, dev->of_offset,
+	fifo_depth = fdtdec_get_int(gd->fdt_blob, dev_of_offset(dev),
 				    "fifo-depth", 0);
 	if (fifo_depth < 0) {
 		printf("DWMMC: Can't get FIFO depth\n");
@@ -79,7 +79,7 @@
 
 	host->name = dev->name;
 	host->ioaddr = (void *)dev_get_addr(dev);
-	host->buswidth = fdtdec_get_int(gd->fdt_blob, dev->of_offset,
+	host->buswidth = fdtdec_get_int(gd->fdt_blob, dev_of_offset(dev),
 					"bus-width", 4);
 	host->clksel = socfpga_dwmci_clksel;
 
@@ -92,9 +92,9 @@
 	host->bus_hz = clk;
 	host->fifoth_val = MSIZE(0x2) |
 		RX_WMARK(fifo_depth / 2 - 1) | TX_WMARK(fifo_depth / 2);
-	priv->drvsel = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+	priv->drvsel = fdtdec_get_uint(gd->fdt_blob, dev_of_offset(dev),
 				       "drvsel", 3);
-	priv->smplsel = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+	priv->smplsel = fdtdec_get_uint(gd->fdt_blob, dev_of_offset(dev),
 					"smplsel", 0);
 	host->priv = priv;