hrtimers/posix-timers: Merge nanosleep timespec copyout logics into a new helper

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-7-viro@ZenIV.linux.org.uk

include/linux/hrtimer.h

@@ -452,6 +452,8 @@ static inline u64 hrtimer_forward_now(struct hrtimer *timer,
 }
 
 /* Precise sleep: */
+
+extern int nanosleep_copyout(struct restart_block *, struct timespec *);
 extern long hrtimer_nanosleep(struct timespec64 *rqtp,
 			      const enum hrtimer_mode mode,
 			      const clockid_t clockid);