Some xHCI hosts contain a "redriver" from TI that silently drops port
status connect changes if the port slips into Compliance Mode.  If the
port slips into compliance mode while the host is in D0, there will not
be a port status change event.  If the port slips into compliance mode
while the host is in D3, the host will not send a PME.  This includes
when the system is suspended (S3) or hibernated (S4).

If this happens when the system is in S3/S4, there is nothing software
can do.  Other port status change events that would normally cause the
host to wake the system from S3/S4 may also be lost.  This includes
remote wakeup, disconnects and connects on other ports, and overrcurrent
events.  A decision was made to _NOT_ disable system suspend/hibernate
on these systems, since users are unlikely to enable wakeup from S3/S4
for the xHCI host.

Software can deal with this issue when the system is in S0.  A work
around was put in to poll the port status registers for Compliance Mode.
The xHCI driver will continue to poll the registers while the host is
runtime suspended.  Unfortunately, that means we can't allow the PCI
device to go into D3cold, because power will be removed from the host,
and the config space will read as all Fs.

Disable D3cold in the xHCI PCI runtime suspend function.

This patch should be backported to kernels as old as 3.2, that
contain the commit 71c731a2 "usb: host:
xhci: Fix Compliance Mode on SN65LVPE502CP Hardware"
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: stable@vger.kernel.org