added the two modules to the cpio and this to the init script:

install_g_serial()                                                                                                                                           
{                                                                                                                                                            
        $INSMOD /lib/modules/2.6.22.1-omap1/kernel/drivers/usb/musb/musb_hdrc.ko mode_default=2                                                              
        $INSMOD /lib/modules/2.6.22.1-omap1/kernel/drivers/usb/gadget/g_serial.ko use_acm=1                                                                  
        sleep 2                                                                                                                                              
        mknod /dev/ttyGS0 c 127 0                                                                                                                            
        cat /proc/kmsg >/dev/ttyGS0 &                                                                                                                        
}