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/gpio/hsdk-creg-gpio.c b/drivers/gpio/hsdk-creg-gpio.c
index d40365e..66f8441 100644
--- a/drivers/gpio/hsdk-creg-gpio.c
+++ b/drivers/gpio/hsdk-creg-gpio.c
@@ -165,5 +165,5 @@
 	.ops	= &hsdk_creg_gpio_ops,
 	.probe	= hsdk_creg_gpio_probe,
 	.of_match = hsdk_creg_gpio_ids,
-	.platdata_auto	= sizeof(struct hsdk_creg_gpio),
+	.plat_auto	= sizeof(struct hsdk_creg_gpio),
 };