tpm: enhance read_log_of() to support Physical TPM event log

Physical TPMs use Open Firmware Device Tree bindings that are similar
to the IBM Power virtual TPM to support event log. However, these
properties store the values in different endianness for Physical
and Virtual TPM.

This patch fixes the endianness issue by doing appropriate conversion
based on Physical or Virtual TPM.

Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Kenneth Goldman <kgold@linux.vnet.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>