sched/smp: Always define sched_domains_mutex_lock()/unlock(), def_root_domain and...

sched/smp: Always define sched_domains_mutex_lock()/unlock(), def_root_domain and sched_domains_mutex

Simplify the scheduler by making CONFIG_SMP=y primitives and data
structures unconditional.

Unconditionally build kernel/sched/topology.c and the main sched-domains
locking primitives.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20250528080924.2273858-20-mingo@kernel.org