[HVM] Update ACPI tables to reflect new PIRQ routing:

[HVM] Update ACPI tables to reflect new PIRQ routing:
 1. Override ISA IRQs 5,6,10,11 as active-low level-triggered.
    These are 'wired' to PCI devices.
 2. Limit PCI-ISA link routers to route to 5,6,10,11. Others
    are active-high edge-triggered and so invalid to use for
    PCI devices. In any case, four ISA IRQs is sufficient to
    avoid unnecessary aliasing among four links.
Also remove PCI device 0 IRQ info. It's an embedded host bridge with
no interrupt sources.

Signed-off-by: Keir Fraser <keir@xensource.com>