TPM: integrity fix

Fix to function which is called by IMA, now tpm_chip_find_get() considers the case in which the machine doesn't have a TPM or, if it has, its TPM isn't enabled.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>