Adds pci id constants which will be used by q35.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>