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/spi/atcspi200_spi.c b/drivers/spi/atcspi200_spi.c
index 9917b54..0f05158 100644
--- a/drivers/spi/atcspi200_spi.c
+++ b/drivers/spi/atcspi200_spi.c
@@ -309,7 +309,7 @@
 
 static int atcspi200_spi_claim_bus(struct udevice *dev)
 {
-	struct dm_spi_slave_platdata *slave_plat =
+	struct dm_spi_slave_plat *slave_plat =
 		dev_get_parent_plat(dev);
 	struct udevice *bus = dev->parent;
 	struct nds_spi_slave *ns = dev_get_priv(bus);