PCI: Clear Secondary Status errors after enumeration

We enumerate devices by attempting config reads to the Vendor ID of each
possible device.  On conventional PCI, if no device responds, the read
terminates with a Master Abort (PCI r3.0, sec 6.1).  On PCIe, the config
read is terminated as an Unsupported Request (PCIe r6.0, sec 2.3.2,
7.5.1.3.7).  In either case, if the read addressed a device below a bridge,
it is logged by setting "Received Master Abort" in the bridge Secondary
Status register.

Clear any errors logged in the Secondary Status register after enumeration.

Link: https://lore.kernel.org/r/20240116143258.483235-1-vidyas@nvidia.com


Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
[bhelgaas: simplify commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>