Well done on connecting directly to the port! That port is ttymxc0 on the device I think. If you want to run a terminal on that port, I suggest trying the getty command, something like this:
/sbin/getty -n -l /bin/sh 115200 ttymxc0 vt102
As for what I did, yeah, I compiled a version of g_serial (otg usb). However, to use it, you must unload g_file_storage and then load g_serial. If you do that, tinyhttp won't run successfully. Also, see the README file.
Since you're connected directly to the serial/debug port, you should be able to do a getty to get a shell on it on boot, which will work even with tinyhttp running.
Does this help you?