This bubbles all the way up to pci_enable_device().
This allows IRQ0 to be used as a legal PCI device IRQ.

The ES7000 uses an interrupt source override to assign pin20 to IRQ0.
Then platform_rename_gsi assigns pin0 a high-numbered IRQ -- available
for PCI devices.  But IRQ0 needs to be a legal PCI IRQ in the lookup code
to make it as far as the re-name code. 
Signed-off-by: Natalie Protasevich <Natalie.Protasevich@UNISYS.com>
Signed-off-by: Len Brown <len.brown@intel.com>