staging: comedi: contec_pci_dio: use attach_pci callback

Convert this PCI driver to use the comedi PCI auto config attach
mechanism by adding an attach_pci callback function. Since the
driver does not require any external configuration options, disable
the legacy attach by making the attach simply return -ENOSYS. This
removes the need to walk to pci bus to find the pci_dev and the
need for the pci_dev_put in the detach.

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