cli: Add menu for hush parser

For the moment, the menu contains only entry: HUSH_OLD_PARSER which is the
default.
The goal is to prepare the field to add a new hush parser which guarantees
actual behavior is still correct.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Francis Laniel <francis.laniel@amarulasolutions.com>