GBA SIO: Fix writing to RCNT
GBA SIO: Fix writing to RCNT

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