chio: Add SPDX-License-Identifier tags

Some BSD-4-Clause files under bin/chio were missing the
SPDX-License-Identifier-tag.

Reviewed by: emaste
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D55193

(cherry picked from commit b6824fe48e4197877f472268859ffe80d7fd946b)