powerpc: ppc4xx: Use CONFIG_OF_CONTROL for canyonlands boards

Enable CONFIG_OF_CONTROL so that U-Boot on these three boards uses a device
tree for its configuration.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/glacier_ramboot_defconfig b/configs/glacier_ramboot_defconfig
index 4fc2303..e5b402e 100644
--- a/configs/glacier_ramboot_defconfig
+++ b/configs/glacier_ramboot_defconfig
@@ -3,3 +3,6 @@
 CONFIG_4xx=y
 CONFIG_TARGET_CANYONLANDS=y
 CONFIG_GLACIER=y
+CONFIG_DEFAULT_DEVICE_TREE="glacier"
+CONFIG_OF_CONTROL=y
+CONFIG_OF_SEPARATE=y