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/broadcom/bcm28155_ap/bcm28155_ap.c b/board/broadcom/bcm28155_ap/bcm28155_ap.c
index 8761638..40ced1a 100644
--- a/board/broadcom/bcm28155_ap/bcm28155_ap.c
+++ b/board/broadcom/bcm28155_ap/bcm28155_ap.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <asm/io.h>
 #include <asm/mach-types.h>
 #include <env.h>