node_device: detect CCW devices
    
    Make CCW devices available to the node_device driver. The devices are
    already seen by udev so let's implement necessary code for detecting
    them properly.
    
    Topologically, CCW devices are similar to PCI devices, e.g.:
    
        +- ccw_0_0_1a2b
            |
            +- scsi_host0
                |
                +- scsi_target0_0_0
                    |
                    +- scsi_0_0_0_0
    
    Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
    Signed-off-by: Bjoern Walk <bwalk@linux.vnet.ibm.com>