Needs a more recent openocd than is currently available in openwrt/packages:
opkg update
wget https://kevinmehall.net/tmp/openocd_d3c2679bcb8e8ba25e7b6e443b39f57474afc099-2_ramips_24kec.ipk -O /tmp/openocd.ipk
opkg install /tmp/openocd.ipk
rm /tmp/openocd.ipk
In another terminal: