hwclock: fix wrong comparison of time value (when it will overlow int)

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/util-linux/hwclock.c b/util-linux/hwclock.c
index 6b4e29b..379eeb2 100644
--- a/util-linux/hwclock.c
+++ b/util-linux/hwclock.c
@@ -43,7 +43,7 @@
 		while (1) {
 			rtc_read_tm(&tm_time, fd);
 			gettimeofday(sys_tv, NULL);
-			if (before != tm_time.tm_sec)
+			if (before != (int)tm_time.tm_sec)
 				break;
 		}
 	}