compositor: Avoid using weston_log() in weston_view_is_opaque()

As from commit b7e5f10bf4, weston_view_is_opaque() is called from
debug_scene_graph_cb(), which on its own represents a (different)
scope. By default, we already have a subscriber for the 'log' scope,
which will cause a harmless, yet spurious, message.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

libweston/compositor.c

@@ -1888,10 +1888,8 @@ weston_view_is_opaque(struct weston_view *ev, pixman_region32_t *region)
 	if (ev->surface->is_opaque)
 		return true;
 
-	if (ev->transform.dirty) {
+	if (ev->transform.dirty)
-		weston_log("%s: transform dirty", __func__);
 		return false;
-	}
 
 	pixman_region32_init(&r);
 	pixman_region32_subtract(&r, region, &ev->transform.opaque);