radv/amdgpu: Split gang submissions correctly when not chained.

radv/amdgpu: Split gang submissions correctly when not chained.

In a gang submit, the follower (typically ACE) and leader
(typically GFX) can have synchronization between each other.
We must ensure that these end up in the same submission,
otherwise we can deadlock the GPU.

We rely on radv_queue here to order follower before the leader
in the submitted CS array.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22354>