tpm/tpm_tis: remove unused itpm variable

Fixes the warning:
drivers/char/tpm/tpm_tis_core.c:443:7: warning: variable ‘itpm’ set but
not used [-Wunused-but-set-variable]
  bool itpm;
       ^~~~

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Acked-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>