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-sunxi/dram_sun4i.c b/arch/arm/mach-sunxi/dram_sun4i.c
index 396c042..72de807 100644
--- a/arch/arm/mach-sunxi/dram_sun4i.c
+++ b/arch/arm/mach-sunxi/dram_sun4i.c
@@ -21,6 +21,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <asm/io.h>
 #include <asm/arch/clock.h>
 #include <asm/arch/dram.h>