pci: apply workaround for Intel errata HSE43 and BDF2/BDX2

pci: apply workaround for Intel errata HSE43 and BDF2/BDX2

These errata affect the values read from the BAR registers, and could
render vPCI (and by extension PVH Dom0 unusable).

HSE43 is a Haswell erratum where a non-BAR register is implemented at
the position where the first BAR of the device should be found in a
Power Control Unit device. Note that there are no BARs on this device,
apart from the bogus CSR register positioned on top of the first BAR.

BDF2/BDX2 is a Broadwell erratum where BARs in the Home Agent device
will return bogus non-zero values.

In both cases the solution is to treat such devices as having no BARs
in the vPCI code.

Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>