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/samsung/smdkv310/smdkv310.c b/board/samsung/smdkv310/smdkv310.c
index 0eba7b6..05369d2 100644
--- a/board/samsung/smdkv310/smdkv310.c
+++ b/board/samsung/smdkv310/smdkv310.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <asm/gpio.h>
 #include <asm/io.h>
 #include <netdev.h>