st/dri: make sure software color-buffers are linear

Otherwise, we might end up with a tiling-capable driver creating a
tiled resource here instead of linear. This is currently possible with
Zink, although we currently force all display-targets to be linear.

But that doesn't seem like a good idea in the long run, so let's loosen
this restriction.

Acked-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2678>
1 file changed