tpm-v2: allow algorithm name to be configured for pcr_read and pcr_extend

For pcr_read and pcr_extend commands allow the digest algorithm to be
specified by an additional argument. If not specified it will default to
SHA256 for backwards compatibility.

Additionally update test_tpm2.py for the changes in output in pcr_read
which now shows the algo and algo length in the output.

A follow-on to this could be to extend all PCR banks with the detected
algo when the <digest_algo> argument is 'auto'.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>