drm/sched: Consolidate drm_sched_rq_select_entity_rr

drm/sched: Consolidate drm_sched_rq_select_entity_rr

Extract out two copies of the identical code to
drm_sched_rq_select_entity_rr()'s epilogue to make it smaller and more
readable.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <phasta@kernel.org>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
[phasta: commit message]
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20250708122121.75689-1-tvrtko.ursulin@igalia.com