drm/sched: Remove racy hack from drm_sched_fini()

drm/sched: Remove racy hack from drm_sched_fini()

drm_sched_fini() contained a hack to work around a race in amdgpu.
According to AMD, the hack should not be necessary anymore. In case
there should have been undetected users,

commit 975ca62a014c ("drm/sched: Add warning for removing hack in drm_sched_fini()")

had added a warning one release cycle ago.

Thus, it can be derived that the hack can be savely removed by now.

Remove the hack.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20260108083019.63532-2-phasta@kernel.org