drm: close the drm file descriptor when the compositor is destroyed

src/compositor-drm.c

@@ -2260,6 +2260,8 @@ drm_destroy(struct weston_compositor *ec)
 		weston_log("failed to drop master: %m\n");
 	tty_destroy(d->tty);
 
+	close(d->drm.fd);
+
 	free(d);
 }