tpm: delete the TPM_TIS_CLK_ENABLE flag

This flag is only used to warn if CLKRUN_EN wasn't disabled on Braswell
systems, but the only way this can happen is if the code is not correct.

So it's an unnecessary check that just makes the code harder to read.

Suggested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.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>