spl: Add support for passing handoff info to U-Boot proper

There is some basic informaton that SPL normally wants to pass through to
U-Boot, such as the SDRAM size and bank information.

Mkae use of the new bloblist structure for this. Add a new 'handoff' blob
which is set up in SPL and passed to U-Boot proper. Also adda  test for
sandbox_spl that checks that this works correctly and a new 'sb' command
to show the information passed from SPL.

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Simon Glass <sjg@chromium.org>

include/spl.h

@@ -11,6 +11,7 @@
 /* Platform-specific defines */
 #include <linux/compiler.h>
 #include <asm/spl.h>
+#include <handoff.h>
 
 /* Value in r0 indicates we booted from U-Boot */
 #define UBOOT_NOT_LOADED_FROM_SPL	0x13578642