You will probably need to make a change in the corresponding .dtsi file and [re]build the image.
In the similar situation I had to make the following adjustment:
Thanks for the reply! I'm running a custom openwrt build, so I don't have the web gui available.
I'll take a look at the dtsi file. I do want the first ethernet LED controlled by the system, since I'm using that port, but I want to control the other ones discretely.