graphics mode: osd: can't turn off (but that state is also not handled by system menu yet)

If you go into the graphics mode settings and turn off OSD it says off for a few frames and then snaps back to on.

Disabling OSD might break the system menu*, so when fixing this make also sure that OSD is turned back on temporarily when the user enters it.

If the option doesn't make much sense with the current state of flow3r anymore we could also remove it.

*the long hold OS button one. We should come up with proper terminology someday.