When changing transferfunction the look-up-tables needs to be
regenerated.
Pick-to: 6.1 6.0 5.15
Change-Id: I83ca5fe570f85d478a374f52c0a82db84e70c3b8
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>