common: Drop init.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arc/lib/init_helpers.c b/arch/arc/lib/init_helpers.c
index c853f25..023eae1 100644
--- a/arch/arc/lib/init_helpers.c
+++ b/arch/arc/lib/init_helpers.c
@@ -3,6 +3,7 @@
  * Copyright (C) 2013-2015 Synopsys, Inc. All rights reserved.
  */
 
+#include <init.h>
 #include <asm/cache.h>
 #include <common.h>