- Add workaround for the problematic PnP BIOS which does not assign
irq resource for the PS/2 mouse device node; if there is no irq
assigned for the PS/2 mouse node, refer to device.hints for an
irq number. If we still don't find an irq number in the hints
database, use a hard-coded value.
- Delete unused ivars.
- Bit of clean up in probe/attach.
- Add PnP ID for the PS/2 mouse port on some IBM ThinkPad models.