tpm: Export tpm2_get_cc_attrs_tbl for ibmvtpm driver as module

This patch fixes the following problem when the ibmvtpm driver
is built as a module:

ERROR: modpost: "tpm2_get_cc_attrs_tbl" [drivers/char/tpm/tpm_ibmvtpm.ko] undefined!
make[1]: *** [scripts/Makefile.modpost:94: __modpost] Error 1
make: *** [Makefile:1298: modules] Error 2

Fixes: 18b3670d ("tpm: ibmvtpm: Add support for TPM2")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>