staging: comedi: skel: do auto-attachment of PCI devices

staging: comedi: skel: do auto-attachment of PCI devices

This driver is an example of how to write a Comedi driver and includes
some code for handling PCI devices, but not very much.  It calls
`comedi_pci_auto_config()` at PCI probe time.  That normally expects to
call the comedi driver's `auto_attach()` hook (or the deprecated
`attach_pci()` hook), but will fall back to using the `attach()` hook
that should only be used for attaching devices "manually" via the
`COMEDI_DEVCONFIG` ioctl.

Add an `auto_attach()` hook (`skel_auto_attach()`) to handle
auto-attachment of supported PCI devices.  Add comments to the
`attach()` hook (`skel_attach()`) to indicate that it shouldn't
generally allow PCI devices to be attached that way (and probably isn't
needed at all for PCI-only Comedi drivers).  Add code to the `detach()`
hook (`skel_detach()`) to disable PCI devices enabled by the
`auto_attach()` hook.

`skel_auto_attach()` calls new function `skel_find_pci_board()` to find
a matching element in `skel_boards[]`.  PCI device ID information has
been added to `skel_boards[]` to give the function something to look
for.

Remove the `pci_dev` member of `struct skel_private` as drivers now use
the `hw_dev` member of `struct comedi_device` to get at the PCI device.

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