time/jiffies: Make clocksource_jiffies static

Commit f1b8274 ("clocksource: Cleanup clocksource selection") removed all
external references to clocksource_jiffies so there is no need to have the
symbol globally visible.

Fixes the following sparse warning:
  CHECK   kernel/time/jiffies.c kernel/time/jiffies.c:61:20: warning: symbol 'clocksource_jiffies' was not declared. Should it be static?

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 6629bf7..25f5b26 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -58,7 +58,7 @@
 	return (cycle_t) jiffies;
 }
 
-struct clocksource clocksource_jiffies = {
+static struct clocksource clocksource_jiffies = {
 	.name		= "jiffies",
 	.rating		= 1, /* lowest valid rating*/
 	.read		= jiffies_read,