timer: Add helper function stopwatch_wait_until_expired

Change-Id: Ia888907028d687e3d17e5a088657086a3c839ad3
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/21589
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/timer.h

@@ -165,6 +165,15 @@ static inline int stopwatch_expired(struct stopwatch *sw)
 	return !mono_time_before(&sw->current, &sw->expires);
 }
 
+/*
+ * Tick and check the stopwatch as long as it has not expired.
+ */
+static inline void stopwatch_wait_until_expired(struct stopwatch *sw)
+{
+	while (!stopwatch_expired(sw))
+		;
+}
+
 /*
  * Return number of microseconds since starting the stopwatch.
  */