staging: comedi: s626: use comedi_pci_detach()

Use comedi_pci_detach() to handle the boilerplate part of the (*detach)
for this PCI driver.

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>