posix-timers: Rename do_schedule_next_timer

That function is a misnomer. Rename it with a proper prefix to
posixtimer_rearm().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.811362578@linutronix.de

kernel/signal.c

@@ -630,7 +630,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
 		 * about to disable them again anyway.
 		 */
 		spin_unlock(&tsk->sighand->siglock);
-		do_schedule_next_timer(info);
+		posixtimer_rearm(info);
 		spin_lock(&tsk->sighand->siglock);
 	}
 #endif