Optimize TLB invalidation

From https://patchwork.freedesktop.org/patch/600784/?series=135341&rev=1#comment_1093612

` Longterm I think we need explore coalescing TLB invalidations targeting the same VM when pressure exists (VM bind case, [1] should help here a bit) or optimize out invalidations (GGTT case, at one point I had logic in for this but pulled it out as it was buggy).

I say this because when debugging [2] I found that lots of TLB invalidations can overwhelm the GuC to the point where it can barely make forward progess on submissions.

The former is likely a fairly large refactor, while the latter shouldn't be too difficult.

Something for us to keep in mind as a group.

Matt `