tpm_tis: further simplify calculation of ordinal duration

commit 07b133e6 ("char/tpm: simplify duration calculation and
eliminate smatch warning.") includes a misleading test that is always
false. The tpm_ordinal_duration table is only valid for TPM_PROTECTED
ordinals where the higher 16 bits are all 0, anyway.

Signed-off-by: Martin Wilck <Martin.Wilck@ts.fujitsu.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Peter Huewe <peterhuewe@gmx.de>