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/arch/arm/mach-orion5x/dram.c b/arch/arm/mach-orion5x/dram.c
index b52c417..33f65db 100644
--- a/arch/arm/mach-orion5x/dram.c
+++ b/arch/arm/mach-orion5x/dram.c
@@ -10,6 +10,7 @@
 
 #include <common.h>
 #include <config.h>
+#include <init.h>
 #include <asm/arch/cpu.h>
 
 DECLARE_GLOBAL_DATA_PTR;