panfrost: Don't reserve space in the color buffer for disabled RTs

Render targets that have no clear or draws are disabled and thus don't
use the color buffer. Don't reserve space for those.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9907>

src/gallium/drivers/panfrost/pan_mfbd.c

@@ -424,6 +424,9 @@ pan_internal_cbuf_size(struct panfrost_batch *batch, unsigned *tile_size)
         for (int cb = 0; cb < batch->key.nr_cbufs; ++cb) {
                 struct pipe_surface *surf = batch->key.cbufs[cb];
 
+                if (!((batch->clear | batch->draws) & (PIPE_CLEAR_COLOR0 << cb)))
+                        surf = NULL;
+
                 if (!surf)
                         continue;