Helper time_support: const function arguments

duration_elapsed and duration_kbps will not modify the struct duration
passed as function argument, hence it should be declared const.

Change-Id: I459c396952c78e907257e2c2f2c630abde92aaa8
Signed-off-by: Alexander Kurz <akurz@blala.de>
Reviewed-on: http://openocd.zylin.com/3232
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

src/helper/time_support.c

@@ -78,14 +78,14 @@ int duration_measure(struct duration *duration)
 	return retval;
 }
 
-float duration_elapsed(struct duration *duration)
+float duration_elapsed(const struct duration *duration)
 {
 	float t = duration->elapsed.tv_sec;
 	t += (float)duration->elapsed.tv_usec / 1000000.0;
 	return t;
 }
 
-float duration_kbps(struct duration *duration, size_t count)
+float duration_kbps(const struct duration *duration, size_t count)
 {
 	return count / (1024.0 * duration_elapsed(duration));
 }

src/helper/time_support.h

@@ -55,8 +55,8 @@ int duration_start(struct duration *duration);
 int duration_measure(struct duration *duration);
 
 /** @returns Elapsed time in seconds. */
-float duration_elapsed(struct duration *duration);
+float duration_elapsed(const struct duration *duration);
 /** @returns KB/sec for the elapsed @a duration and @a count bytes. */
-float duration_kbps(struct duration *duration, size_t count);
+float duration_kbps(const struct duration *duration, size_t count);
 
 #endif	/* TIME_SUPPORT_H */