comedi vmk80xx: support comedi auto-configuration

Add support for automatically associating a vmk8055 device with a
comedi device (previously the user had to use comedi_num_legacy_minors
to reserve device slots and then associate them with vmk8055 devices
using comedi_config).
Tested on multiple K8055s, but not on K8061s.

Signed-off-by: J. Ali Harlow <ali@avrc.city.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>