sched/headers: Move the sched_exec() prototype to <linux/sched/task.h>

sched_exec() better fits into the task lifetime APIs than into the core scheduler
APIs.

This reduces the size of <linux/sched.h> a bit.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched/task.h

@@ -77,6 +77,13 @@ extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
 
 extern void free_task(struct task_struct *tsk);
 
+/* sched_exec is called by processes performing an exec */
+#ifdef CONFIG_SMP
+extern void sched_exec(void);
+#else
+#define sched_exec()   {}
+#endif
+
 #define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0)
 
 extern void __put_task_struct(struct task_struct *t);