staging: comedi: amplc_dio200: allow generation of PCIe interrupts

The new PCIe boards PCIe215, PCIe236 and PCIe296 need a special register
setting to allow generation of interrupts on the PCIe bus.  Add
`dio200_pcie_board_setup()` to do this and call it from
`dio200_attach_pci()` for those boards.

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