You have to manually modify the device tree (dtb) by hand to remove or disable that regulator. https://boot.libre.computer/ci/roc-rk3328-cc.dts
The ldto command will generate a dtb file and place it in /boot/efi. You need to convert it with device tree compiler, dtc, to the dts format and then edit it and then convert it back into a dtb. Please note that this has implications on other parts of the system that relies on the same regulator. You have to check the Libre Computer Board Hardware Schematics Links to see which other devices are using the same regulator.