kernel/time/timekeeping.c: cleanups

- remove the no longer required __attribute__((weak)) of xtime_lock
- remove the following no longer used EXPORT_SYMBOL's:
  - xtime
  - xtime_lock

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/time.h b/include/linux/time.h
index 6a5f503..b04136d 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -92,7 +92,7 @@
 
 extern struct timespec xtime;
 extern struct timespec wall_to_monotonic;
-extern seqlock_t xtime_lock __attribute__((weak));
+extern seqlock_t xtime_lock;
 
 extern unsigned long read_persistent_clock(void);
 extern int update_persistent_clock(struct timespec now);