[Cin] AMD's amf in ffmpeg

[Andrea paz]

In Arch amf requires amdgpu-pro, which is very problematic though. I
have read that amf will be included in ROCm using vulkan and at that
point will no longer need the proprietary drivers. I've always had
problems with amdgpu-pro so I don't use them.

I tried using:

env AMD_VULKAN_ICD=RADV ./cinelerra5/cinelerra-5.1/bin/cin

and I don't get any errors but the video card doesn't activate and
therefore, I think, vulkan doesn't work. If I try to play with CinGG
video drivers I get a freeze that forces me to close the program.

I'll wait when everything is more stable and working to test, but I
don't have much confidence in AMF (as also with vulkan).