panfrost: Don't use lower_wpos_pntc on Midgard

gl_PointCoord is implemented via a special attribute descriptor on Midgard. This descriptor has an orientation bit, the orientation is driver-controlled. That means we can map rast->sprite_coord_mode to this bit, rather than lowering in the shader.

This is a bug fix for point sprites, which are implemented natively on Midgard for dubious reasons and need to be flipped this way. It is also an optimization for apps reading gl_PointCoord, removing the extra arithmetic to flip, although the value of this is somewhat dubious.

Signed-off-by: Alyssa Rosenzweig alyssa@collabora.com Cc: mesa-stable