backend/drm: drop no-op shortcut

Since e5fc8cd4c7 ("output: trigger frame/present events on all
commits on enabled output"), any commit on an enabled output is
supposed to trigger frame/present events.

The DRM backend was skipping the commit completely for no-op
commits. Stop doing so.

Closes: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3719

backend/drm/drm.c

@@ -692,11 +692,6 @@ bool drm_connector_commit_state(struct wlr_drm_connector *conn,
 		return false;
 	}
 
-	if ((base->committed & COMMIT_OUTPUT_STATE) == 0) {
-		// This commit doesn't change the KMS state
-		return true;
-	}
-
 	bool ok = false;
 	struct wlr_drm_connector_state pending = {0};
 	drm_connector_state_init(&pending, conn, base);