It shouldn't harm the SM57, but there is no point in using phantom power with the 57 since the 57 is a dynamic mic and dynamic mics don't use phantom power.
If your phantom power is either on or off to all available channels, and you need it on to power a condenser mic in one channel, and the 57 is plugged into another channel, it should not harm the 57. If all you have plugged in is the 57 (and/or other dynamic mics), just keep the phantom power turned off.