tpm: use more algorithms than sha256 on pcr_read

The current tpm2_pcr_read is hardcoded using SHA256. Make the
actual command to TPM configurable to use wider range of algorithms.
The current command line is kept as is i.e limited to SHA-256 only.

Signed-off-by: Ruchika Gupta <ruchika.gupta@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>