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/atmel/at91sam9rlek/at91sam9rlek.c b/board/atmel/at91sam9rlek/at91sam9rlek.c
index 4e674d4..f81dccc 100644
--- a/board/atmel/at91sam9rlek/at91sam9rlek.c
+++ b/board/atmel/at91sam9rlek/at91sam9rlek.c
@@ -7,6 +7,7 @@
 
 #include <common.h>
 #include <debug_uart.h>
+#include <init.h>
 #include <vsprintf.h>
 #include <asm/io.h>
 #include <asm/mach-types.h>