bdinfo: Show the RAM top and approximate stack pointer

These are useful pieces of information when debugging. The RAM top shows
where U-Boot started allocating memory from, before it relocated. The
stack pointer can be checked to ensure it is in the correct region.

Change-Id: Ib35b8f5950b2eceb28aaf39b527c3463cc5c394f
Signed-off-by: Simon Glass <sjg@chromium.org>
2 files changed