dm: core: Access device ofnode through functions

At present ofnode is present in the device even if it is never used. With
of-platdata this field is not used, so can be removed. In preparation for
this, change the access to go through inline functions.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/gpio/octeon_gpio.c b/drivers/gpio/octeon_gpio.c
index 958516d..42eae79 100644
--- a/drivers/gpio/octeon_gpio.c
+++ b/drivers/gpio/octeon_gpio.c
@@ -190,7 +190,7 @@
 			GPIO_CONST_GPIOS_MASK;
 	} else {
 		priv->base = dev_remap_addr(dev);
-		uc_priv->gpio_count = ofnode_read_u32_default(dev->node,
+		uc_priv->gpio_count = ofnode_read_u32_default(dev_ofnode(dev),
 							      "nr-gpios", 32);
 	}