On Viola V1.2, DC/DC regulator (IC1, AP6503) and USB power switch (IC3, TPS2042BD) are the 2 components are directly connected to the Input power (PWR_IN_FILT power rail) and I expect that these component may / may not fail because of reverse polarity.
I would recommend you to first perform load test on 3.3V power rail (ensure that Colibri module is NOT connected to the carrier board). AP6503 can supply 3A (max) current @ 3.3V. Probe 3.3V power rail to check for any voltage drop and also check if IC1 heats up or not.
If you find the power supply is working fine. Connect the Colibri module and test the USB interface if it is working properly.
Feel free to contact me if you have any question.