x11-drivers/xf86-video-[ati,amdgpu]: update 18.1
Update to the 18.1 release for both ati and amdgpu DDX. ati is still seeing
active development and amdgpu bring, among other things, support for Raven
Ridge APUs.
Reviewed by: x11 (zeising)
Approved by: x11 (zeising)
Differential Revision: https://reviews.freebsd.org/D17332