staging: comedi: adv_pci1724: absorb setup_subdevices()

For aesthetics, absorb this function into the (*auto_attach).

Add some whitespace to the subdevice init.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>