tpm: remove invalid min length check from tpm_do_selftest()

Removal of this check was not properly amended to the original commit.

Cc: stable@vger.kernel.org
Fixes: 0c541332 ("tpm: use tpm_pcr_read_dev() in tpm_do_selftest()")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>