* Add collector for PCIe devices with link information
The link status of PCIe devices sometimes changes,
like link or speed downgrades, and devices disappear.
This patch collects PCIe devices' link infromation to detect such failures.
As a first step, this collector exports PCIe devices'
- Device information (vendor_id, device_id, etc.)
- Parent PCIe device (e.g. PCIe bridge, PCIe switch)
- Link status (max_link_{transfers_per_second|width}, current_link_{transfers_per_second|width})
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Signed-off-by: Naoki MATSUMOTO <m.naoki9911@gmail.com>
