sched/topology: Make sched_energy_mutex,update static

smatch reports
kernel/sched/topology.c:212:1: warning:
  symbol 'sched_energy_mutex' was not declared. Should it be static?
kernel/sched/topology.c:213:6: warning:
  symbol 'sched_energy_update' was not declared. Should it be static?

These variables are only used in topology.c, so should be static

Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20230314144818.1453523-1-trix@redhat.com