Could you also check the power tree “hardware/nvidia/platform/t210/porg/kernel-dts/porg-platforms/tegra210-porg-fixed-p3448-0000-a00.dtsi” and see if it matches your desgin?
On nano devkit, when we plug the DP cable to device, I can see the avdd-io-edp-1v05 is pulled to high.
gpio-511 ( |avdd-io-edp-1v05 ) out hi
Since the case on your side is the HPD has 1v8 but driver gives no response, it seems the power source is incorrect.