tests/tcg: add sha512 test

This imports the sha512 algorithm and related tests from ccan which
offers a cleaner hash implementation with its own validation tests
with which we can exercise TCG code generations.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220225172021.3493923-13-alex.bennee@linaro.org>