staging: comedi: gsc_hpdi: don't store physical base addresses

In `struct hpdi_private`, the `plx9080_phys_iobase` and
`hpdi_phys_iobase` hold the physical memory addresses from the PCI
BARs used by this driver.  The physical addresses are only really needed
when ioremapping the resources when the device is being attached by
`hpdi_auto_attach()`.  A non-zero value of the `hpdi_phys_iobase` is
also used to indicate that a call to `comedi_pci_enable()` was
successful so that `comedi_pci_disable()` should be called when the
device is detached by `hpdi_detach()`.

Remove the `plx9080_phys_iobase` and `hpdi_phys_iobase` members and use
`dev->iobase` as a flag to indicate whether `comedi_pci_disable()` needs
to be called by `hpdi_detach()`.

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