Yeah you can edit the control file located in the firmware folder. The item is on line 1: FW_MINER_HWVER="Antminer S9i". Got a spare control board lying around so gonna test the edit
EDIT: So yeah, don't edit the file. Chances are it will brick the vanilla s9. Can't understand why it does that if using the SD card works but oh well.
Umm it doesn't brick anything by changing the control file to the s9 from s9i. Thats exactly what I did and I have it running on multiple early batch S9s without an issue.