vc4: Don't try to use color load/stores to blit across format changes.

We could potentially support the right combination of 8888 to 565, but the
important thing for now is to not mix up our orderings of 8888.  Fixes
fbo-copyteximage regressions.

src/gallium/drivers/vc4/vc4_blit.c

@@ -138,6 +138,9 @@ vc4_tile_blit(struct pipe_context *pctx, const struct pipe_blit_info *info)
                 return false;
         }
 
+        if (info->dst.resource->format != info->src.resource->format)
+                return false;
+
         struct vc4_surface *dst_surf =
                 vc4_get_blit_surface(pctx, info->dst.resource, info->dst.level);
         struct vc4_surface *src_surf =