AMD SB600 EHCI controller not working

The EHCI controller seems to throw interrupts (e.g. port change) just fine, but after queuing an async request, we never get a completion interrupt.

Things that do not help:

• Applying the SB600/SB700 quirk found in other kernels (http://lxr.free-electrons.com/source/drivers/usb/host/ehci-pci.c?v=3.17#L198)
• A timer that regularly forces manual status bit checks in case interrupts don't fire
• Various minor changes to make our queue entries look more like those Window uses

Problem also exists when using our usbehci.sys on Windows 2003.

cc christoph_vw, j_anderw, aicommander