This is for N2 only!
As a quick change, you can do the following (please test it on SD card first in case your screw up the DTB)
fdtget /flash/dtb.img /gpio-reset/usb_hub gpios
Write down the first number (lets call it X), then:
mount -o rw,remount /flash
fdtput /flash/dtb.img /leds/blueled gpios X 78 0 # X is the first number from the first command
You can run the following command to verify your changes (and to get the original values before making changes)
fdtget /flash/dtb.img /leds/blueled gpios
Then reboot.
The above will map the heartbeat led to pin #8 (GPIOX_12)