Unfortunately, the BSP doesn’t do anything with the OC flag information. It seems that there is not even an interface where you can ask for this information. However, if you need the OC information you can configure the according pin as GPIO4_6 and read the pin status via GPIO interface.
The USB specification doesn’t clearly say what to do in an over current situation. If your power supply has trouble with over current, then you need to power down the power supply immediately without involving the software at all.
Regards,
Stefan