s390/qeth: switch to ccwgroup_create_dev

Switch to the new ccwgroup_create_dev interface. Also wrap device
attributes in a struct device_type and let the driver core create
these attributes automagically.

Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>