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>
diff --git a/common/init/Makefile b/common/init/Makefile
index 4902635..853b56d 100644
--- a/common/init/Makefile
+++ b/common/init/Makefile
@@ -5,3 +5,4 @@
 #
 
 obj-y += board_init.o
+obj-$(CONFIG_$(SPL_TPL_)HANDOFF) += handoff.o