dma-fence: Use a flag for 64-bit seqnos

dma-fence: Use a flag for 64-bit seqnos

With the goal of reducing the need for drivers to touch (and dereference)
fence->ops, we move the 64-bit seqnos flag from struct dma_fence_ops to
the fence->flags.

Drivers which were setting this flag are changed to use new
dma_fence_init64() instead of dma_fence_init().

v2:
 * Streamlined init and added kerneldoc.
 * Rebase for amdgpu userq which landed since.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Christian König <christian.koenig@amd.com> # v1
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://lore.kernel.org/r/20250515095004.28318-3-tvrtko.ursulin@igalia.com