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/rtl8139.c b/drivers/net/rtl8139.c
index 934e0c2..c171e54 100644
--- a/drivers/net/rtl8139.c
+++ b/drivers/net/rtl8139.c
@@ -772,7 +772,7 @@
 	.probe	= rtl8139_probe,
 	.ops	= &rtl8139_ops,
 	.priv_auto	= sizeof(struct rtl8139_priv),
-	.platdata_auto	= sizeof(struct eth_pdata),
+	.plat_auto	= sizeof(struct eth_pdata),
 };
 
 U_BOOT_PCI_DEVICE(eth_rtl8139, supported);