tpm: use tpm2_pcr_read() in tpm2_do_selftest()

tpm2_do_selftest() performs a PCR read during the TPM initialization phase.
This patch replaces the PCR read code with a call to tpm2_pcr_read().

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkine@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>