tpm: fix multiple race conditions in tpm_ppi.c

* Traversal of the ACPI device tree was not done right. It should lookup
  PPI only under the ACPI device that it is associated. Otherwise, it could
  match to a wrong PPI interface if there are two TPM devices in the device
  tree.
* Removed global ACPI handle and version string from tpm_ppi.c as this
  is racy. Instead they should be associated with the chip.
* Added missing copyright platter.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>