Qt: Remove mutable qualifier from VFileDevice now that it isn't needed anymore
Qt: Remove mutable qualifier from VFileDevice now that it isn't needed anymore

Touched/mgba,mgba-emu/mgba,sergiobenrocha2/mgba,Touched/mgba,jeremyherbert/mgba,Anty-Lemon/mgba,libretro/mgba,jeremyherbert/mgba,sergiobenrocha2/mgba,libretro/mgba,MerryMage/mgba,iracigt/mgba,jeremyherbert/mgba,matthewbauer/mgba,iracigt/mgba,cassos/mgba,Iniquitatis/mgba,fr500/mgba,cassos/mgba,sergiobenrocha2/mgba,MerryMage/mgba,jeremyherbert/mgba,Anty-Lemon/mgba,Iniquitatis/mgba,Anty-Lemon/mgba,zerofalcon/mgba,bentley/mgba,askotx/mgba,iracigt/mgba,sergiobenrocha2/mgba,iracigt/mgba,fr500/mgba,bentley/mgba,matthewbauer/mgba,AdmiralCurtiss/mgba,askotx/mgba,mgba-emu/mgba,libretro/mgba,libretro/mgba,MerryMage/mgba,Anty-Lemon/mgba,askotx/mgba,cassos/mgba,zerofalcon/mgba,AdmiralCurtiss/mgba,sergiobenrocha2/mgba,Iniquitatis/mgba,mgba-emu/mgba,fr500/mgba,Touched/mgba,Iniquitatis/mgba,libretro/mgba,mgba-emu/mgba,fr500/mgba,zerofalcon/mgba,AdmiralCurtiss/mgba,askotx/mgba