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/net/mvgbe.c b/drivers/net/mvgbe.c
index 0be6715..0e4e88e 100644
--- a/drivers/net/mvgbe.c
+++ b/drivers/net/mvgbe.c
@@ -1042,6 +1042,6 @@
 	.probe	= mvgbe_probe,
 	.ops	= &mvgbe_ops,
 	.priv_auto	= sizeof(struct mvgbe_device),
-	.platdata_auto	= sizeof(struct eth_pdata),
+	.plat_auto	= sizeof(struct eth_pdata),
 };
 #endif /* CONFIG_DM_ETH */