Currently, read_log() has two implementations: one for ACPI platforms
and the other for device tree(OF) based platforms. The proper one is
selected at compile time using Kconfig and #ifdef in the Makefile,
which is not the recommended approach.

This patch removes the #ifdef in the Makefile by defining a single
read_log() method, which checks for ACPI/OF event log properties at
runtime.

[jarkko.sakkinen@linux.intel.com: added tpm_ prefix to read_log*]
Suggested-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: NNayna Jain <nayna@linux.vnet.ibm.com>
Reviewed-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>