um: Fix read_persistent_clock fallout

commit 9f31f57(um: Convert to use read_persistent_clock) moved the
code, but not the variable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 2b8b262..a08d9fa 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -104,15 +104,14 @@
 
 void read_persistent_clock(struct timespec *ts)
 {
-	nsecs = os_nsecs();
+	long long nsecs = os_nsecs();
+
 	set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
 				nsecs % NSEC_PER_SEC);
 }
 
 void __init time_init(void)
 {
-	long long nsecs;
-
 	timer_init();
 	late_time_init = setup_itimer;
 }