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>

drivers/ddr/altera/sdram_agilex.c

@@ -25,7 +25,7 @@ DECLARE_GLOBAL_DATA_PTR;
 
 int sdram_mmr_init_full(struct udevice *dev)
 {
-	struct altera_sdram_plat *plat = dev->plat;
+	struct altera_sdram_plat *plat = dev_get_plat(dev);
 	struct altera_sdram_priv *priv = dev_get_priv(dev);
 	u32 i;
 	int ret;