PCI: make CPU list affinity visible

Stephen Hemminger wrote:
> Looks like Mike created cpulistaffinty in sysfs but never completed
> the job.

This patch hooks things up correctly, taking care to remove the new file
when the bus is destroyed.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>