fix: FN switch, cannot adjust volume when toggled value is "unchanged", hardware indicator mismatch

[mohammadsyuhada]

This should fix these issue for tg5040:

1. When "Volume when toggled" is set to "unchanged", then we activate the FN switch. User cannot adjust the volume, but the brightness, color temperature, contrast, etc can be adjusted.
2. The hardware adjustment indicator showing the current level, not the one configured in the setting. When user specifically set brightness to 0% in setting "Brightness when toggled", then he activate the FN switch, the indicator stay at previous level, not at 0%.

[frysee]

1. Set Mute toggle to "Unchanged"
2. Switch toggle on
3. Start game
4. Audio is now unexpectedly muted
5. Pressing volume+ results in 100% volume
6. Volume overlay updates, but actual volume does not - stays at 100%

[frysee]

In addition to that, I think the current behaviour (outside of bugged volume) is actually more useful than restricting changes when FN is toggled on:

• Toggling FN sets the values as defined in settings
• Vol+/- combo still allows making (temporary) changes when desired
• Toggling FN off again restores the original value