PCI: Avoid FLR for AMD Starship USB 3.0

The AMD Starship USB 3.0 host controller advertises Function Level Reset
support, but it apparently doesn't work.  Add a quirk to prevent use of FLR
on this device.

Without this quirk, when attempting to assign (pass through) an AMD
Starship USB 3.0 host controller to a guest OS, the system becomes
increasingly unresponsive over the course of several minutes, eventually
requiring a hard reset.  Shortly after attempting to start the guest, I see
these messages:

  vfio-pci 0000:05:00.3: not ready 1023ms after FLR; waiting
  vfio-pci 0000:05:00.3: not ready 2047ms after FLR; waiting
  vfio-pci 0000:05:00.3: not ready 4095ms after FLR; waiting
  vfio-pci 0000:05:00.3: not ready 8191ms after FLR; waiting

And then eventually:

  vfio-pci 0000:05:00.3: not ready 65535ms after FLR; giving up
  INFO: NMI handler (perf_event_nmi_handler) took too long to run: 0.000 msecs
  perf: interrupt took too long (642744 > 2500), lowering kernel.perf_event_max_sample_rate to 1000
  INFO: NMI handler (perf_event_nmi_handler) took too long to run: 82.270 msecs
  INFO: NMI handler (perf_event_nmi_handler) took too long to run: 680.608 msecs
  INFO: NMI handler (perf_event_nmi_handler) took too long to run: 100.952 msecs
  ...
  watchdog: BUG: soft lockup - CPU#3 stuck for 22s! [qemu-system-x86:7487]

Tested on a Micro-Star International Co., Ltd. MS-7C59/Creator TRX40
motherboard with an AMD Ryzen Threadripper 3970X.

Link: https://lore.kernel.org/r/20200524003529.598434ff@f31-4.lan
Signed-off-by: Kevin Buettner <kevinb@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

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