uboot-phytec

sandbox: Add 'sb' command to access filesystem features

The new 'sb' command is intended to deal with sandbox-specific features
that have no parallel in other archs. This commit adds two sub-commands
to list a directory and read a file from the host filesystem.

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