s390: Use ccw_device_get_id() in qeth/claw drivers

Use ccw_device_get_id() to get a device number
instead of parsing the ccw device's bus id.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Frank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>