A function that has not finished resetting answers configuration
requests with all ones. pcie_flr() read PCIER_DEVICE_STA once after a
fixed sleep and so reported a transaction that does not exist:

pci0:9:0:0: Transactions pending after FLR!

pci_power_reset() waited only the 10 ms that pci_set_powerstate()
applies leaving D3.

The stale report is the smaller problem: callers restore configuration
state as soon as the reset returns, and a restore into a function that
is not answering is lost, leaving the BARs and command register clear.

Poll for the function to answer before returning.

PR: 296662