BIOS Unlocking for AMD VRAM option

Hi,
I have an Asus Zenbook Flip 14 and there is no option to change the amount of VRAM the AMD Radeon (integrated video card) takes. I would like to unlock the bios options because at the moment my VRAM is set by default to 2 GB, meaning I can use only 5.9/8 GB.
Is there a way to do this? Looking back some discussions in the forum it can be done.
Thanks