dm: treewide: Rename dev_get_platdata() to dev_get_plat()

Rename this to be consistent with the change from 'platdata'.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/demo/demo-simple.c b/drivers/demo/demo-simple.c
index 950e286..39b370c 100644
--- a/drivers/demo/demo-simple.c
+++ b/drivers/demo/demo-simple.c
@@ -14,7 +14,7 @@
 
 static int simple_hello(struct udevice *dev, int ch)
 {
-	const struct dm_demo_pdata *pdata = dev_get_platdata(dev);
+	const struct dm_demo_pdata *pdata = dev_get_plat(dev);
 
 	printf("Hello from %08x: %s %d\n", (uint)map_to_sysmem(dev), pdata->colour,
 	       pdata->sides);