ui/vc slider: fix slider intensity adjustment in level mode
ui/vc slider: fix slider intensity adjustment in level mode

It has to be done on GenericFaders and not at FadeChannels

sbenejam/qlcplus,kripton/qlcplus,plugz/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,plugz/qlcplus,kripton/qlcplus,sbenejam/qlcplus,kripton/qlcplus,plugz/qlcplus,sbenejam/qlcplus,kripton/qlcplus,mcallegari/qlcplus,kripton/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,mcallegari/qlcplus,plugz/qlcplus,mcallegari/qlcplus,plugz/qlcplus,kripton/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,plugz/qlcplus,sbenejam/qlcplus,kripton/qlcplus,plugz/qlcplus,mcallegari/qlcplus