drm/sched: Drain all entities in DRM sched run job worker

All entities must be drained in the DRM scheduler run job worker to
avoid the following case. An entity found that is ready, no job found
ready on entity, and run job worker goes idle with other entities + jobs
ready. Draining all ready entities (i.e. loop over all ready entities)
in the run job worker ensures all job that are ready will be scheduled.

Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Closes: https://lore.kernel.org/all/CABXGCsM2VLs489CH-vF-1539-s3in37=bwuOWtoeeE+q26zE+Q@mail.gmail.com/


Reported-and-tested-by: Mario Limonciello <mario.limonciello@amd.com>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3124
Link: https://lore.kernel.org/all/20240123021155.2775-1-mario.limonciello@amd.com/


Reported-and-tested-by: Vlastimil Babka <vbabka@suse.cz>
Closes: https://lore.kernel.org/dri-devel/05ddb2da-b182-4791-8ef7-82179fd159a8@amd.com/T/#m0c31d4d1b9ae9995bb880974c4f1dbaddc33a48a


Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240124210811.1639040-1-matthew.brost@intel.com