sched/headers: Constify object_is_on_stack()

object_is_on_stack() doesn't modify its argument and should never do it.
Make it const.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel@pengutronix.de
Link: http://lkml.kernel.org/r/20171205104415.17147-1-s.hauer@pengutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched/task_stack.h

@@ -78,7 +78,7 @@ static inline void put_task_stack(struct task_struct *tsk) {}
 #define task_stack_end_corrupted(task) \
 		(*(end_of_stack(task)) != STACK_END_MAGIC)
 
-static inline int object_is_on_stack(void *obj)
+static inline int object_is_on_stack(const void *obj)
 {
 	void *stack = task_stack_page(current);