board_f: Make init_helpers generic

This header file is used by two archs. It could be used by all of them
since it allows the cache to be on during relocation. Move it into a
generic file.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/init_helpers.h

@@ -0,0 +1,18 @@
+/*
+ * (C) Copyright 2011
+ * Graeme Russ, <graeme.russ@gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _INIT_HELPERS_H_
+#define _INIT_HELPERS_H_
+
+/**
+ * init_cache_f_r() - Turn on the cache in preparation for relocation
+ *
+ * @return 0 if OK, -ve on error
+ */
+int init_cache_f_r(void);
+
+#endif	/* _INIT_HELPERS_H_ */