llvmpipe: Eliminate color buffer swizzling.

llvmpipe: Eliminate color buffer swizzling.

Now dead code.

Also had to remove the show_tiles/show_subtiles because now the color
buffers are always stored in their native format, so there is no longer
an easy way to paint the tile sizes.

Depth-stencil buffers are still swizzled.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>