[SRU][Artful] using vfio-pci on a combination of cn8xxx and some PCI devices results in a kernel panic

[Manoj Iyer]

Bug: https://launchpad.net/bugs/1770254

Please consider these three patches cherry-picked cleanly from upstream
for SRU to Artful. On Cavium cn8xxx systems, using vfio-pci on a
combination of cn8xxx and some PCI devices results in a kernel panic.
This is triggered by issuing a bus or a slot reset on the PCI device,
and observed when you pass through a PCI device from host to guest. 

These patches are already in Bionic, we need these patches in Artful so 
that xenial linux-hwe also has the fix. The platforms of interest were 
certified with Xenial and linux-hwe, so we are interested in fixing this 
only in Artful.

A test kernel is available in ppa:manjo/lp1770254 and was tested by me
on a Cavium CN88XX system, and results are posted to the bug report.