GB I/O: Fix bootrom running forever
GB I/O: Fix bootrom running forever

libretro/mgba,Iniquitatis/mgba,Iniquitatis/mgba,Iniquitatis/mgba,Iniquitatis/mgba,mgba-emu/mgba,libretro/mgba,mgba-emu/mgba,libretro/mgba,fr500/mgba,fr500/mgba,mgba-emu/mgba,libretro/mgba,Anty-Lemon/mgba,Anty-Lemon/mgba,mgba-emu/mgba,Anty-Lemon/mgba,libretro/mgba,Anty-Lemon/mgba,fr500/mgba,fr500/mgba