Fix the Not button showing up in the advanced control dialog.

The Not button isn't supposed to show up on outputs to controllers.
When we generate the button it still shows up if it isn't added to the sizer since the parent window still owns it.

Fixes this issue report https://forums.dolphin-emu.org/Thread-linux-ui-bug-in-gc-pad-configuration-menu?pid=335269#pid335269
Merge pull request #816 from Sonicadvance1/fix-not-button

Fix the Not button showing up in the advanced control dialog.