staging: comedi: amplc_dio200: Fix PCI ref count

When attaching a PCI device manually via the comedi driver `attach` hook
(`dio200_attach()`) (called by the comedi core for the
`COMEDI_DEVCONFIG` ioctl), its reference count is incremented in the
`for_each_pci_dev` loop (in `dio200_find_pci_dev()`).  It is decremented
when the `detach` hook (`dio200_detach()`) is called to detach the
device.  However, when the PCI device is attached automatically via the
`attach_pci` hook (`dio200_attach_pci()`, called at probe time via
`comedi_pci_auto_config()`) it's reference count is not incremented so
there will be an unmatched decrement when detaching the device.

Increment the PCI device reference count in `dio200_attach_pci()` to
correct the mismatch.

Once support for manual configuration has been removed from this driver,
the calls to `pci_dev_get()` and `pci_dev_put()` can be removed.

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