gallium: Add a block depth field to the u_formats table.

gallium: Add a block depth field to the u_formats table.

To add ASTC 3D compression formats, we need to be able to express the
block depth.  While I'm touching every line, line up the columns of
the CSV again as they've drifted over time.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>