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/at91sam9n12ek/at91sam9n12ek.c b/board/atmel/at91sam9n12ek/at91sam9n12ek.c
index 51b24e1..90d3235 100644
--- a/board/atmel/at91sam9n12ek/at91sam9n12ek.c
+++ b/board/atmel/at91sam9n12ek/at91sam9n12ek.c
@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <vsprintf.h>
 #include <asm/io.h>
 #include <asm/arch/at91sam9x5_matrix.h>