dma-buf/dma-fence: remove unnecessary callbacks

dma-buf/dma-fence: remove unnecessary callbacks

The fence_value_str and timeline_value_str callbacks were just an
unnecessary abstraction in the SW sync implementation.

The only caller of those callbacks already knew that the fence in
questions is a timeline_fence. So print the values directly instead
of using a redirection.

Additional to that remove the implementations from virtgpu and vgem.
As far as I can see those were never used in the first place.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20250211163109.12200-3-christian.koenig@amd.com