How to increase VRAM and Open Hardware Acceleration of AMD APU

Hi. I'm trying to make a hackintosh on my HP Probook 455G9 with AMD 5825U APU (Vega 8 Integrated). The problem is BIOS is locked for changing the VRAM even though I have 16GB RAM and NootedRed. Therefore, I can't increase the stock VRAM which is 512mb currently. I tried using Smokeless UMAF but the option for changing the VRAM didn't show up there. What is the way to increase VRAM in this case?