vmm: emulate INVD by ignoring it

[corvink]

Summary

On physical systems the ram isn't initialized on boot. So, coreboot uses
the cache as ram in this boot phase. When exiting cache as ram, coreboot
calls INVD for making the cache consistent.

In a virtual environment ram is always initialized and the cache is
always consistent. So, we can safely ignore this call.

[jhb]

Presumably there aren't other uses of invd for which we would want some sort of behavior? But I suspect the reasons for ignoring wbinvd are similar.

[corvink]

If I don't miss something, INVD is always senseless in a virtual environment. So, I'm not planning to implement some kind of emulation.