RetroPie: Splashscreen Sound Fix for USB Audio

Edit the file /opt/retropie/supplementary/splashscreen/asplashscreen.sh and change the line:

omxplayer -o both -b --layer 10000 "$line"

to

omxplayer -o alsa -b --layer 10000 "$line

On some earlier systems the file is /etc/init.d/asplashscreen.