clockevents/source: Use u64 to make 32bit happy

unsigned long is not 64bit on 32bit machine.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index d9d5f8c..1c95fd6 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -639,7 +639,7 @@
  */
 void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
 {
-	unsigned long sec;
+	u64 sec;
 
 	/*
 	 * Calc the maximum number of seconds which we can run before