Rework TTMs busy handling

[Christian König]

Hi guys,

I'm trying to make this functionality a bit more useful for years now
since we multiple reports that behavior of drivers can be suboptimal
when multiple placements be given.

So basically instead of hacking around the TTM behavior in the driver
once more I've gone ahead and changed the idle/busy placement list
into idle/busy placement flags. This not only saves a bunch of code,
but also allows setting some placements as fallback which are used if
allocating from the preferred ones didn't worked.

Zack pointed out that some removed VMWGFX code was brought back because
of rebasing, fixed in this version.

Intel CI seems to be happy with those patches, so any more comments?

Regards,
Christian.