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/board/armltd/total_compute/total_compute.c b/board/armltd/total_compute/total_compute.c
index 0be6435..35e8743 100644
--- a/board/armltd/total_compute/total_compute.c
+++ b/board/armltd/total_compute/total_compute.c
@@ -17,7 +17,7 @@
 
 U_BOOT_DEVICE(total_compute_serials) = {
 	.name = "serial_pl01x",
-	.platdata = &serial_platdata,
+	.plat = &serial_platdata,
 };
 
 static struct mm_region total_compute_mem_map[] = {