xfree86: Support Moore Threads GPU
During testing Moore Threads GPU with ubuntu lightdm+gnome+xorg desktop environment, we found that it can load DDX with mtgpu_drv.so. But during screen locking, lightdm will start a new Xorg to display a greeter, this new Xorg would match modesettings_drv.so instead of a correct one mtgpu_drv.so.
After debuging, we found the root cause is that xf86VideoPtrToDriverList function of Xorg is absent support for Moore Threads GPU.
Edited by Peng Jin