dm: treewide: Rename ..._platdata variables to just ..._plat

Try to maintain some consistency between these variables by using _plat as
a suffix for them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/ddr/altera/sdram_s10.c b/drivers/ddr/altera/sdram_s10.c
index 8028d89..984dc32 100644
--- a/drivers/ddr/altera/sdram_s10.c
+++ b/drivers/ddr/altera/sdram_s10.c
@@ -70,7 +70,7 @@
  */
 int sdram_mmr_init_full(struct udevice *dev)
 {
-	struct altera_sdram_platdata *plat = dev->plat;
+	struct altera_sdram_plat *plat = dev->plat;
 	struct altera_sdram_priv *priv = dev_get_priv(dev);
 	u32 update_value, io48_value, ddrioctl;
 	u32 i;