Many of the AM335x terminals default to GPIO mode after power is applied. See the description of bits [2:0] of the respective conf_<module>_<pin> register.
The GPIOs default to input mode after reset, but may have internal pull-up or pull-downs enabled while reset is applied and these pull-up or pull-down resistors may remain enabled after reset is released.
I assume the reset signal you need connected to one of the AM335x GPIOs is active-low open-drain with an external pull-up and/or a few internal pull-ups in the attached devices. If so, you should select one of the available AM335x GPIOs that has the internal pull-up enabled by default rather than one with a pull-down enable by default. You do not want a pull-down in AM335x to be fighting the other pull-ups connected to this signal.
You can configure the AM335x GPIO to operate like a open-drain output by permanently setting the respective bit in the GPIO_DATAOUT register low (0) and using the respective bit in the GPIO_OE register to toggle between output disabled (1) and output enabled (0). However, you need to make sure your software never configures the respective bit of GPIO_DATAOUT register high (1) while the respective bit in the GPIO_OE register is enabled (0) and another device is driving the signal low.
Regards,
Paul