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: NBoris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Signed-off-by: NBjoern Walk <bwalk@linux.vnet.ibm.com>