tpm2: Add BIGUM parameter to BigInitialized and use VERIFY in TpmToOsslMath.c

tpm2: Add BIGUM parameter to BigInitialized and use VERIFY in TpmToOsslMath.c

The original TPM 2 version of BIG_INITIALIZED uses a BIGNUM
on the stack and uses the internals of the BIGNUM's data structure
to initialize it. We don't do this here but use only the API
functions and therefor have tp free the BIGNMs create with
BIG_INITIALIZED().

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>