PCI: work around IvyBridge internal graphics FLR erratum

For IvyBridge Mobile platform, a system hang may occur if a FLR (Function
Level Reset) is asserted to internal graphics.

This quirk is a workaround for the IVB FLR errata issue.  We are
disabling the FLR reset handshake between the PCH and CPU display, then
manually powering down the panel power sequencing and resetting the PCH
display.

Signed-off-by: Xudong Hao <xudong.hao@intel.com>
Signed-off-by: Kay, Allen M <allen.m.kay@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>