staging: comedi: cb_pcidas64: use auto_attach method

This driver does not need to support manual attachment of supported PCI
devices.  Replace the `attach()` hook with an `auto_attach()` hook.
This will be called via `comedi_pci_auto_config()` at PCI probe time.

The `auto_attach()` calls new function `cb_pcidas64_find_pci_board()` to
find the correct entry in `pcidas64_boards[]` for the PCI device.

This driver no longer increments the PCI reference count during
attachment, so remove the call to `pci_dev_put()` when detaching the
device.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>