dri: Don't pretend we can lower NV15/NV20 when we can't

If the plane formats are __DRI_IMAGE_FORMAT_NONE (AKA PIPE_FORMAT_NONE),
we can't lower the planar-YUV. I guess this code relies on
::is_format_supported(PIPE_FORMAT_NONE, PIPE_BIND_SAMPLER_VIEW)
returning false, but it's not obvious to me that it should, and panfrost
has been returning true on this one for quite a long time. It could be
that panfrost is wrong, and this case should be rejected, but it's just
as simple to reject the lowering if the plane format is
__DRI_IMAGE_FORMAT_NONE instead of deferring this check to the driver,
because ultimately we can't lower NV15/NV20 unless the driver supports
NV15/NV20 or R10_G10B10_{420,422}.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35761>

src/gallium/frontends/dri/dri_helpers.c

@@ -762,8 +762,13 @@ dri2_yuv_dma_buf_supported(struct dri_screen *screen,
       return false;
 
    for (unsigned i = 0; i < map->nplanes; i++) {
-      if (!pscreen->is_format_supported(pscreen, map->planes[i].dri_format,
-            screen->target, 0, 0, PIPE_BIND_SAMPLER_VIEW))
+      /* Some planar-YUV formats can't be lowered unless the HW supports
+       * specific YUV-as-RGB formats. Those have their plane format set
+       * to __DRI_IMAGE_FORMAT_NONE. */
+      if (map->planes[i].dri_format == __DRI_IMAGE_FORMAT_NONE ||
+          !pscreen->is_format_supported(pscreen, map->planes[i].dri_format,
+                                        screen->target, 0, 0,
+                                        PIPE_BIND_SAMPLER_VIEW))
          return false;
    }
    return true;