Upgrading from pre-Hedy will lead to missing UCI-section for GPIO-control

[SvenRoederer]

This is based on #591, where @bobster-galore pointed out that such upgrades will not create the UCI-section that a fresh install will make for this PoE-out.

Indeed it sounds more like an upstream-issue, but let's keep it as reminder here.

Edit: in the original issue @pmelange pointed out, that user-scripts might conflict with the UCI-settings also.