drm/amdgpu: fix missing dma_fence_put in error path

When the fence can't be added we need to drop the reference.

Suggested-by: Bert Karwatzki <spasswolf@web.de>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230105111703.52695-2-christian.koenig@amd.com


Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>