conf: Drop needless setting of VIR_DOMAIN_TPM_VERSION_DEFAULT

conf: Drop needless setting of VIR_DOMAIN_TPM_VERSION_DEFAULT

In previous commit the VIR_DOMAIN_TPM_VERSION_DEFAULT value was
made just an alias to value of 0. And since all newly allocated
memory is zeroed out (due to use of g_new0()), the def->version
inside of virDomainTPMDefParseXML() is also 0 and thus there is
no need to set it explicitly.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>