ASoC: cros_ec_codec: switch to library API for SHA-256

The CrOS EC codec driver uses SHA-256 explicitly, and not in a
performance critical manner, so there is really no point in using
the SHASH crypto API here. Let's switch to the library API instead.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
Cc: Cheng-Yi Chiang <cychiang@chromium.org>
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Benson Leung <bleung@chromium.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20200515100309.20795-1-ardb@kernel.org


Signed-off-by: Mark Brown <broonie@kernel.org>