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/fsl_qspi.c b/drivers/spi/fsl_qspi.c
index 089c2d8..fc3b844 100644
--- a/drivers/spi/fsl_qspi.c
+++ b/drivers/spi/fsl_qspi.c
@@ -515,7 +515,7 @@
 
 static void fsl_qspi_select_mem(struct fsl_qspi *q, struct spi_slave *slave)
 {
-	struct dm_spi_slave_platdata *plat =
+	struct dm_spi_slave_plat *plat =
 		dev_get_parent_plat(slave->dev);
 
 	if (q->selected == plat->cs)