Dear Penguins,

As a follow up on my own post ( http://lkml.org/lkml/2008/6/18/195 ), I
have  solved a small bug/misbehavior within the pci_scan_single_device().

The misbehavior manifest itself upon calling pci_scan_child_bus() with a
bus which already contain some devices. After scanning is done devices
that already existed will be present twice in the PCI bus devise list.
Once with is_added indication and once without. Trying to add this bus
will cause a resource conflict as the same device is already present and
initialized.

This patch will simply prevent a device to be added to a pci bus list if 
it is already there.

Points to consider:
1. I am not a PCI Guru and might have over looked the bigger picture. Is
it OK to prevent a device of being re-added?
2. I have decided that two devices are, in fact, the same instance if it
has the same: vendor, device, and devfn. Is there a finer test for a
device identity?

p.s. As per http://www.kernel.org/pub/linux/docs/lkml/#s1-10 it is
preferred for Mozilla Firefox clients to attach the patch, hence my
patch is attached.

Liberty

Signed-off-by: Eran Liberty <liberty@extricom.org>
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