rtl_test: fix build on Mac OS

Thanks to mot for reporting.
closes #3130

Signed-off-by: Steve Markgraf <[email protected]>

Author: steve-m

Diff for: src/rtl_test.c

@@ -162,8 +162,8 @@ static int ppm_gettime(struct time_generic *tg)
 	struct timeval tv;
 
 	rv = gettimeofday(&tv, NULL);
-	ts->tv_sec = tv.tv_sec;
-	ts->tv_nsec = tv.tv_usec * 1000;
+	tg->tv_sec = tv.tv_sec;
+	tg->tv_nsec = tv.tv_usec * 1000;
 #endif
 	return rv;
 }