radv: fix memory leak of descriptor set layout

radv: fix memory leak of descriptor set layout

We need to be able to track the descriptor sets explicity to unref the
descriptor sets, otherwise these descriptor sets will not unref the
descriptor set layout it holds.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6222
Fixes: 66f7289d568
("radv: add reference counting for descriptor set layouts")

Tested-by: Jakob Bornecrantz <jakob@collabora.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15741>