staging: comedi: adl_pci9118: use 'context' in (*auto_attach)

The pci_device_id 'driver_data' is passed as the 'context' when the (*auto_attach)
mechanism is used to attach this driver. Add a boardid enum and index the boardinfo
so that the "pci9118dg" boardinfo is automatically selected. This allow removing
the pci9118_find_boardinfo() helper.

Unfortunately all the boards supported by this driver have the same device id.
Add commented out entries in the device table for them.

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>