dm: treewide: Rename 'platdata' variables to just 'plat'

We use 'priv' for private data but often use 'platdata' for platform data.
We can't really use 'pdata' since that is ambiguous (it could mean private
or platform data).

Rename some of the latter variables to end with 'plat' for consistency.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/demo/demo-simple.c b/drivers/demo/demo-simple.c
index bf71466..950e286 100644
--- a/drivers/demo/demo-simple.c
+++ b/drivers/demo/demo-simple.c
@@ -43,5 +43,5 @@
 	.id	= UCLASS_DEMO,
 	.ofdata_to_platdata = demo_shape_ofdata_to_platdata,
 	.ops	= &simple_ops,
-	.platdata_auto	= sizeof(struct dm_demo_pdata),
+	.plat_auto	= sizeof(struct dm_demo_pdata),
 };