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/spi/tegra20_slink.c b/drivers/spi/tegra20_slink.c
index b99ef38..3057fe1 100644
--- a/drivers/spi/tegra20_slink.c
+++ b/drivers/spi/tegra20_slink.c
@@ -95,7 +95,7 @@
 
 static int tegra30_spi_of_to_plat(struct udevice *bus)
 {
-	struct tegra_spi_plat *plat = bus->plat;
+	struct tegra_spi_plat *plat = dev_get_plat(bus);
 	const void *blob = gd->fdt_blob;
 	int node = dev_of_offset(bus);
 
@@ -314,7 +314,7 @@
 
 static int tegra30_spi_set_speed(struct udevice *bus, uint speed)
 {
-	struct tegra_spi_plat *plat = bus->plat;
+	struct tegra_spi_plat *plat = dev_get_plat(bus);
 	struct tegra30_spi_priv *priv = dev_get_priv(bus);
 
 	if (speed > plat->frequency)