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})
Signed-off-by: Naoki MATSUMOTO <m.naoki9911@gmail.com>