fbd-dev-led: Move multicolor handling to separate class

Everything related to multicolor moves into the new class and we add the
necessary getters and setters so derived classes can access the parent
classes attributes where needed.

src/fbd-dev-led-priv.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2023 Purism SPC
+ *
+ * SPDX-License-Identifier: GPL-3.0+
+ */
+#pragma once
+
+#include "fbd-dev-led.h"
+#include "fbd-feedback-led.h"
+
+#include <gudev/gudev.h>
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define LED_MAX_BRIGHTNESS_ATTR  "max_brightness"
+
+GUdevDevice      *fbd_dev_led_get_device  (FbdDevLed *led);
+void              fbd_dev_led_set_max_brightness (FbdDevLed *led, guint max_brightness);
+void              fbd_dev_led_set_color (FbdDevLed *led, FbdFeedbackLedColor color);
+
+G_END_DECLS