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>

The old 'sb' command was deprecated in 2015 and replaced with 'host'. It
is useful to be able to access some internal sandbox state, particularly
for testing.

Resurrect the old command and provide a way to print some basic state
information (currently just the arguments to sandbox).

Signed-off-by: Simon Glass <sjg@chromium.org>