i965: Make the CopyImage BLT path bail for stencil images.

The BLT can't handle S8 because it's W-tiled (at least without
additional funny business, and I'm not sure we care).  Disallow
it so it falls back to the CPU path, which works.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>

src/mesa/drivers/dri/i965/intel_copy_image.c

@@ -48,6 +48,9 @@ copy_image_with_blitter(struct brw_context *brw,
    if (src_mt->num_samples > 0 || dst_mt->num_samples > 0)
       return false;
 
+   if (src_mt->format == MESA_FORMAT_S_UINT8)
+      return false;
+
    /* According to the Ivy Bridge PRM, Vol1 Part4, section 1.2.1.2 (Graphics
     * Data Size Limitations):
     *