time: Kill xtime_lock, replacing it with jiffies_lock

Now that timekeeping is protected by its own locks, rename
the xtime_lock to jifffies_lock to better describe what it
protects.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/drivers/clocksource/i8253.c b/drivers/clocksource/i8253.c
index e7cab2d..14ee3ef 100644
--- a/drivers/clocksource/i8253.c
+++ b/drivers/clocksource/i8253.c
@@ -35,7 +35,7 @@
 
 	raw_spin_lock_irqsave(&i8253_lock, flags);
 	/*
-	 * Although our caller may have the read side of xtime_lock,
+	 * Although our caller may have the read side of jiffies_lock,
 	 * this is now a seqlock, and we are cheating in this routine
 	 * by having side effects on state that we cannot undo if
 	 * there is a collision on the seqlock and our caller has to