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/CarMediaLab/flea3/flea3.c b/board/CarMediaLab/flea3/flea3.c
index be0bc22..fb66c9e 100644
--- a/board/CarMediaLab/flea3/flea3.c
+++ b/board/CarMediaLab/flea3/flea3.c
@@ -8,6 +8,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <asm/io.h>
 #include <env.h>
 #include <linux/errno.h>