linux-imx

drm/amdgpu: remove fence fallback

DC doesn't seem to have a fallback path either.

So when interrupts doesn't work any more we are pretty much busted no
matter what.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>