freedreno: Fix leak of binning shader variants.

The v->binning variant is never added to shader->variants, so just free
each one as we free the nonbinning variant.

Noticed from drm-shim mode running out of open fds, since each bo ends up
with an fd.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4502>

src/freedreno/ir3/ir3_shader.c

@@ -48,6 +48,8 @@ delete_variant(struct ir3_shader_variant *v)
 		ir3_destroy(v->ir);
 	if (v->bo)
 		fd_bo_del(v->bo);
+	if (v->binning)
+		delete_variant(v->binning);
 	free(v);
 }