Move initf_malloc() to a common place

To allow this function to be used from SPL, move it to the malloc()
code.

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

include/malloc.h

@@ -906,6 +906,9 @@ void *realloc_simple(void *ptr, size_t size);
 
 #endif
 
+/* Set up pre-relocation malloc() ready for use */
+int initf_malloc(void);
+
 /* Public routines */
 
 /* Simple versions which can be used when space is tight */