tpm_nsc: Fix bug when loading multiple TPM drivers

This patch fixes kernel bugzilla 34572.

https://bugzilla.kernel.org/show_bug.cgi?id=34572



Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reported-by: Witold Baryluk <baryluk@smp.if.uj.edu.pl>
Tested-by: Witold Baryluk <baryluk@smp.if.uj.edu.pl>
Signed-off-by: James Morris <jmorris@namei.org>