[S390] cio: allow offline processing for disconnected devices

When disconnected ccw devices are removed, the device has to be set
offline, otherwise there will be side effects including a reference
count imbalance. This patch modifies ccw_device_offline to work for
devices in disconnecte/not operational state. ccw_device_offline is
called by cio for devices which are online during device removal.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>