ISDN: Convert from class_device to device for ISDN capi

Signed-off-by: Tony Jones <tonyj@suse.de>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>