rcu: Include torture_sched_setaffinity() declaration

The prototype for torture_sched_setaffinity() will be moved to a
different header, which will need to be included from update.c to avoid
this W=1 warning:

kernel/rcu/update.c:529:6: error: no previous prototype for 'torture_sched_setaffinity' [-Werror=missing-prototypes]
  529 | long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Author: arndb

kernel/rcu/update.c

@@ -25,6 +25,7 @@
 #include <linux/interrupt.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/debug.h>
+#include <linux/torture.h>
 #include <linux/atomic.h>
 #include <linux/bitops.h>
 #include <linux/percpu.h>