stop_machine: Make stop_cpus() static

The function stop_cpus() is only used internally by the
stop_machine for stop multiple cpus.

Make it static.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191228161912.24082-1-tiny.windzz@gmail.com
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 5d68ec4..865bb02 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -442,7 +442,7 @@ static int __stop_cpus(const struct cpumask *cpumask,
  * @cpumask were offline; otherwise, 0 if all executions of @fn
  * returned 0, any non zero return value if any returned non zero.
  */
-int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
+static int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
 {
 	int ret;