PCI/DPC: Disable DPC service on suspend

PCI/DPC: Disable DPC service on suspend

If the link is powered off during suspend, electrical noise may cause
errors that trigger DPC.  If the DPC interrupt is enabled and shares an IRQ
with PME, that causes a spurious wakeup during suspend.

Disable DPC triggering and the DPC interrupt during suspend to prevent
this.  Clear DPC interrupt status before re-enabling DPC interrupts during
resume so we don't get an interrupt for errors that occurred during the
suspend/resume process.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=209149
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218090
Link: https://lore.kernel.org/r/20240416043225.1462548-3-kai.heng.feng@canonical.com
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
[bhelgaas: clear status on resume, add comments, commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>