vp_vdpa: fix id_table array not null terminated error

Allocate one extra virtio_device_id as null terminator, otherwise
vdpa_mgmtdev_get_classes() may iterate multiple times and visit
undefined memory.

Fixes: ffbda8e9 ("vdpa/vp_vdpa : add vdpa tool support in vp_vdpa")
Cc: stable@vger.kernel.org
Suggested-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Angus Chen <angus.chen@jaguarmicro.com>
Signed-off-by: Xiaoguang Wang <lege.wang@jaguarmicro.com>
Message-Id: <20241105133518.1494-1-lege.wang@jaguarmicro.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Acked-by: Jason Wang <jasowang@redhat.com>