selftest/firmware: Add selftest timeout in settings

The firmware tests would always time out for me. Add a correct timeout,
including details on how the value was reached. Additionally allow the
test harness to skip comments in settings files and report how long a
given timeout was.

Reviewed-by: SeongJae Park <sjpark@amazon.de>
Acked-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200724213640.389191-3-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>