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/lib/acpi/acpi_device.c b/lib/acpi/acpi_device.c
index 52b21ce..8efa8e9 100644
--- a/lib/acpi/acpi_device.c
+++ b/lib/acpi/acpi_device.c
@@ -724,7 +724,7 @@
 static int acpi_device_set_spi(const struct udevice *dev, struct acpi_spi *spi,
 			       const char *scope)
 {
-	struct dm_spi_slave_platdata *plat;
+	struct dm_spi_slave_plat *plat;
 	struct spi_slave *slave = dev_get_parent_priv(dev);
 
 	plat = dev_get_parent_plat(slave->dev);