feedback-vibra: Allow derived classes to override duration

This allows the derived classes to perform the length duration
calculation.  The parent class can thus still keep track of the total
feedback length.

Signed-off-by: Guido Günther <agx@sigxcpu.org>

src/fbd-feedback-vibra-priv.h

@@ -0,0 +1,14 @@
+/*
+ * Copyright (C) 2024 The Phosh Developers
+ *
+ * SPDX-License-Identifier: GPL-3.0+
+ */
+#pragma once
+
+#include <fbd-feedback-vibra.h>
+
+G_BEGIN_DECLS
+
+void fbd_feedback_vibra_set_duration (FbdFeedbackVibra *self, guint duration);
+
+G_END_DECLS