posix-timers: Make nanosleep timespec argument const

No nanosleep implementation modifies the rqtp argument. Mark is const.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>

kernel/time/alarmtimer.c

@@ -753,7 +753,7 @@ static long __sched alarm_timer_nsleep_restart(struct restart_block *restart)
  * Handles clock_nanosleep calls against _ALARM clockids
  */
 static int alarm_timer_nsleep(const clockid_t which_clock, int flags,
-			      struct timespec64 *tsreq)
+			      const struct timespec64 *tsreq)
 {
 	enum  alarmtimer_type type = clock2alarm(which_clock);
 	struct restart_block *restart = &current->restart_block;