[coreboot] [AMD family16h] What need to be done in coreboot to support the Virtual Wire mode

[Zheng Bao]

Hi, all,
I need to support VxWorks in Virtual Wire mode. The code is stable in coreboot.org for a long time which supports
Windows and Linux.
I add code to set the Interrupt Line in PciConfiguration space.
What else needs to be done?

Zheng