drm/sched: Update timedout_job()'s documentation

drm/sched: Update timedout_job()'s documentation

drm_sched_backend_ops.timedout_job()'s documentation is outdated. It
mentions the deprecated function drm_sched_resubmit_jobs(). Furthermore,
it does not point out the important distinction between hardware and
firmware schedulers.

Since firmware schedulers typically only use one entity per scheduler,
timeout handling is significantly more simple because the entity the
faulted job came from can just be killed without affecting innocent
processes.

Update the documentation with that distinction and other details.

Reformat the docstring to work to a unified style with the other
handles.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250305130551.136682-5-phasta@kernel.org