First of all, we were not forcing the pixmap to be moved in before
attempting to present it. Secondly, in certain configurations, we avoid
ever backing pixmaps with vram (in GPUs with 32MB of VRAM or less).
This fixes the observed cases where we ended up assuming that a bo was
backing a pixmap
Commit 8c8f15c9d3 added increased pitch alignment requirements to handle
nv10-nv40 tiling (which must have a small number * PoT pitch). While
NV4/NV5 do have tiling, this was never supported in nouveau.
This change enables 1920x1200 resolutions since the maximum surface
pitch has to be strictly
