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/test/dm/test-driver.c b/test/dm/test-driver.c
index 5c074cd..b9f49de 100644
--- a/test/dm/test-driver.c
+++ b/test/dm/test-driver.c
@@ -21,7 +21,7 @@
 
 static int testdrv_ping(struct udevice *dev, int pingval, int *pingret)
 {
-	const struct dm_test_pdata *pdata = dev_get_platdata(dev);
+	const struct dm_test_pdata *pdata = dev_get_plat(dev);
 	struct dm_test_priv *priv = dev_get_priv(dev);
 
 	*pingret = pingval + pdata->ping_add;