PCI: pciehp: Ignore belated Presence Detect Changed caused by DPC

Commit c3be50f7 ("PCI: pciehp: Ignore Presence Detect Changed caused by
DPC") sought to ignore Presence Detect Changed events occurring as a side
effect of Downstream Port Containment.

The commit awaits recovery from DPC and then clears events which occurred
in the meantime.  However if the first event seen after DPC is Data Link
Layer State Changed, only that event is cleared and not Presence Detect
Changed.  The object of the commit is thus defeated.

That's because pciehp_ist() computes the events to clear based on the local
"events" variable instead of "ctrl->pending_events".  The former contains
the events that had occurred when pciehp_ist() was entered, whereas the
latter also contains events that have accumulated while awaiting DPC
recovery.

In practice, the order of PDC and DLLSC events is arbitrary and the delay
in-between can be several milliseconds.

So change the logic to always clear PDC events, even if they come after an
initial DLLSC event.

Fixes: c3be50f7 ("PCI: pciehp: Ignore Presence Detect Changed caused by DPC")
Reported-by: Lương Việt Hoàng <tcm4095@gmail.com>
Reported-by: Joel Mathew Thomas <proxy0@tutamail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219765#c165


Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Lương Việt Hoàng <tcm4095@gmail.com>
Tested-by: Joel Mathew Thomas <proxy0@tutamail.com>
Link: https://patch.msgid.link/d9c4286a16253af7e93eaf12e076e3ef3546367a.1750257164.git.lukas@wunner.de