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/posix-timers.h

@@ -10,7 +10,7 @@ struct k_clock {
 	int	(*clock_adj)(const clockid_t which_clock, struct timex *tx);
 	int	(*timer_create)(struct k_itimer *timer);
 	int	(*nsleep)(const clockid_t which_clock, int flags,
-			  struct timespec64 *);
+			  const struct timespec64 *);
 	int	(*timer_set)(struct k_itimer *timr, int flags,
 			     struct itimerspec64 *new_setting,
 			     struct itimerspec64 *old_setting);