For ports which are configured as present, pull-up resistors external to the hub are required. There are no internal resistors on the OVRx# pins, so without termination resistors the inputs can float can cause a false over current condition.
If you have disabled the port through the configuration control, external resistors are not required but are recommended. When the port is disabled through the configuration the hub will disable the port and the port status is not reported, but floating inputs can allow noise to be feed into the chip.
The OVR# is an input that can be set to be active low or active high and should be terminated to a state appropriate for the configuration chosen.