dm: Use access methods for dev/uclass private data

Most drivers use these access methods but a few do not. Update them.

In some cases the access is not permitted, so mark those with a FIXME tag
for the maintainer to check.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Pratyush Yadav <p.yadav@ti.com>
diff --git a/drivers/serial/sandbox.c b/drivers/serial/sandbox.c
index c7d5390..a05c564 100644
--- a/drivers/serial/sandbox.c
+++ b/drivers/serial/sandbox.c
@@ -72,7 +72,7 @@
 
 static int sandbox_serial_remove(struct udevice *dev)
 {
-	struct sandbox_serial_plat *plat = dev->plat;
+	struct sandbox_serial_plat *plat = dev_get_plat(dev);
 
 	if (plat->colour != -1)
 		output_ansi_reset();
@@ -83,7 +83,7 @@
 static int sandbox_serial_putc(struct udevice *dev, const char ch)
 {
 	struct sandbox_serial_priv *priv = dev_get_priv(dev);
-	struct sandbox_serial_plat *plat = dev->plat;
+	struct sandbox_serial_plat *plat = dev_get_plat(dev);
 
 	/* With of-platdata we don't real the colour correctly, so disable it */
 	if (!CONFIG_IS_ENABLED(OF_PLATDATA) && priv->start_of_line &&
@@ -203,7 +203,7 @@
 
 static int sandbox_serial_of_to_plat(struct udevice *dev)
 {
-	struct sandbox_serial_plat *plat = dev->plat;
+	struct sandbox_serial_plat *plat = dev_get_plat(dev);
 	const char *colour;
 	int i;