virtio_pci: Use self group type for cap commands

Section 2.12.1.2 of v1.4 of the VirtIO spec states:

The device and driver capabilities commands are currently defined for
self group type.
1. VIRTIO_ADMIN_CMD_CAP_ID_LIST_QUERY
2. VIRTIO_ADMIN_CMD_DEVICE_CAP_GET
3. VIRTIO_ADMIN_CMD_DRIVER_CAP_SET

Fixes: bfcad518 ("virtio: Manage device and driver capabilities via the admin commands")
Signed-off-by: Daniel Jurgens <danielj@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Message-Id: <20250304161442.90700-1-danielj@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>