intel: Rely on mesa core for compressed texture image uploading.

intel: Rely on mesa core for compressed texture image uploading.

There's nothing in our normal texture path we need for this.  We don't
PBO upload blit it.  We don't need to worry about flushing because
MapTextureImage handles it.  hiz scattergather doesn't apply, but MTI
handles it too.

Acked-by: Kenneth Graunke <kenneth@whitecape.org>