PCI: Wait for up to 1000ms after FLR reset

Some devices take longer than the spec indicates to return from FLR reset,
a notable case of this is Intel integrated graphics (IGD), which can often
take an additional 300ms powering down an attached LCD panel as part of the
FLR.  Allow devices up to 1000ms, testing every 100ms whether the second
dword of config space is read as -1.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>