nvfx: new 2D: rewrite miptree code, adapt transfers

nvfx: new 2D: rewrite miptree code, adapt transfers

Changes:
- Disable swizzling on non-RGBA 2D textures, since the current 2D
  code is mostly broken in those cases. A later patch will fix this.
  Thanks to Andrew Randrianasulu who reported this.
- Fix compressed texture transfers and hack around the current 2D
  code inability to copy compressed textures by using direct access.
  Thanks to Andrew Randrianasulu who reported this.

This patch rewrites all the miptree layout and transfer code in the
nvfx driver.

The current code is broken in several ways:
1. 3D textures are laid out first by face, then by level, which is
incorrect
2. Cube maps should have 128-byte aligned faces
3. Swizzled textures have a strange alignment test that seems
unnecessary
4. We store the image_offsets for each face/slice but they can be
easily computed instead
5. "Swizzling" is not supported for compressed formats. They can be
"swizzled" but swizzling only means that there are no gaps (pitch is
level-dependant) and the layout is still linear
6. Swizzling is not supported for non-RGBA formats. All formats (except
possibly depth) can be swizzled according to my testing.

The miptree layout is rewritten based on my empirical testing, which I
posted in the "miptree findings" mail.
The image_offset array is removed, since it can be calculated with a
simple multiplication; the only array in the miptree structure is now
the one for mipmap level starts, which it seems cannot be easily
computed in constant time.

Also, we now directly store a nouveau_bo instead of a pipe_buffer in
the miptree structure, like nv50 does.

Support for render temporaries is removed, and will be readded in a
later patch.

Note that the current temporary code is broken, because it does not
copy the temporary back on render cache flushes.