Make sure that the cdev pointer for IO subchannels is set to NULL when
we deregister the device (and release its last reference). This will
fix a bug were another process operates on an already freed ccw device.
Acked-by: NPeter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>