P9_26 is inconsistent in the P9 pin table and the PRU table.
Created by: MarkAYoder
https://github.com/beagleboard/beaglebone-ai/wiki/System-Reference-Manual#pru-icss2-pin-access shows P9_26 on pru1_0 pin 17 and pru2_1 pin 13.
But https://github.com/beagleboard/beaglebone-ai/wiki/System-Reference-Manual#p9.26-p9.29 only shows it on pin 17. There are no entries for MODES 12 and 13.