hw/ppc/pnv_occ: skip automatic zero-init of large struct

hw/ppc/pnv_occ: skip automatic zero-init of large struct

The 'occ_model_tick' method has a 12k struct used for copying
data between guest and host. Skip the automatic zero-init of this
struct to eliminate the performance overhead in the I/O hot path.

The 'dynamic_data' buffer will be fully initialized when reading
data from the guest.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Message-id: 20250610123709.835102-25-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>