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/mini-box/picosam9g45/picosam9g45.c b/board/mini-box/picosam9g45/picosam9g45.c
index 9a72404..5e55918 100644
--- a/board/mini-box/picosam9g45/picosam9g45.c
+++ b/board/mini-box/picosam9g45/picosam9g45.c
@@ -11,6 +11,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <vsprintf.h>
 #include <asm/io.h>
 #include <asm/arch/clk.h>