New ACPI PCI Link Routing code

[John Baldwin]

I've done some work on the ACPI PCI link code to make it a bit more like $PIR 
in that it is link centric and uses actual new-bus devices for each device 
link.  One benefit of this is that unused links will be disabled now which 
might help with interrupt aliasing problems on machines using APICs.  Also, 
instead of routing IRQs for links via PCI device numbers using tunables, they 
are now routed via the link name ala $PIR.  Thus, one uses 
'hw.pci.link.LNKA.irq=X' to route LNKA to IRQ X.  Also, when choosing a 
virgin interrupt, we no longer try to guess at which IRQs might be used by 
ISA devices.  Instead, we only use known-good IRQs including IRQs that the 
BIOS has already used and the SCI if the link is being routed via ISA IRQs.  
The patch is at http://www.FreeBSD.org/~jhb/patches/acpi_pci_link.patch  
Please test and let me know if there are any problems, thanks.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org