staging: comedi: s626: store the pci_dev in the comedi_device

Use the hw_dev pointer in the comedi_device struct to hold the
pci_dev instead of carrying it in the private data.

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>