Signed-off-by: Wolfgang Denk <wd@denx.de>
[trini: Fixup common/cmd_io.c]
Signed-off-by: Tom Rini <trini@ti.com>

It is difficult to automatically test tracing on most architectures, but
with sandbox it is easy enough to do a simple sanity check.

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