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/usb/host/ehci-atmel.c b/drivers/usb/host/ehci-atmel.c
index 22a35a5..fba3595 100644
--- a/drivers/usb/host/ehci-atmel.c
+++ b/drivers/usb/host/ehci-atmel.c
@@ -124,7 +124,7 @@
 	.probe		= ehci_atmel_probe,
 	.remove		= ehci_deregister,
 	.ops		= &ehci_usb_ops,
-	.plat_auto	= sizeof(struct usb_platdata),
+	.plat_auto	= sizeof(struct usb_plat),
 	.priv_auto	= sizeof(struct ehci_atmel_priv),
 	.flags		= DM_FLAG_ALLOC_PRIV_DMA,
 };