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/drivers/ram/bmips_ram.c b/drivers/ram/bmips_ram.c
index 3e1dd9e..8f953e7 100644
--- a/drivers/ram/bmips_ram.c
+++ b/drivers/ram/bmips_ram.c
@@ -10,6 +10,7 @@
 #include <common.h>
 #include <dm.h>
 #include <errno.h>
+#include <init.h>
 #include <ram.h>
 #include <asm/io.h>