tpm: fix byte-order for the value read by tpm2_get_tpm_pt

The result must be converted from BE byte order, which is used by the
TPM2 protocol. This has not popped out because tpm2_get_tpm_pt() has
been only used for probing.

Fixes: 7a1d7e6d

 ("tpm: TPM 2.0 baseline support")
Change-Id: I7d71cd379b1a3b7659d20a1b6008216762596590
Signed-off-by: Andrey Pronin <apronin@chromium.org>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>