common: Move RAM-sizing functions to init.h

These functions relate to memory init so move them into the init
header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/astro/mcf5373l/mcf5373l.c b/board/astro/mcf5373l/mcf5373l.c
index db157a8..9adf58e 100644
--- a/board/astro/mcf5373l/mcf5373l.c
+++ b/board/astro/mcf5373l/mcf5373l.c
@@ -6,6 +6,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <serial.h>
 #include <watchdog.h>
 #include <command.h>