From the description that you provided I understand that you wish to use I2S in the Rx mode only and thus want to use the data_out pin for another purpose. Please let me know if my understanding of the issue is not correct.
In that case you can disable the Tx option in the I2S configurator as shown in the below:
After you disable the TX the configurator will not ask you to assign pins for the DATA_OUT.
In that case you can use the pin that you had assigned to DATA_OUT for the other functionality that you want.
Please let me know if you have further queries related to this issue.