svc_encoder_rtc: Replace a die() call with fatal()

die() calls usage_exit(). The usage help message doesn't need to be
printed when reporting a frame mismatch.

Bug: aomedia:3404
Change-Id: Ib5b26776f38c188cc6a8febc4e35150539c6d16c
diff --git a/examples/svc_encoder_rtc.c b/examples/svc_encoder_rtc.c
index 1ede1c2..5d8542f 100644
--- a/examples/svc_encoder_rtc.c
+++ b/examples/svc_encoder_rtc.c
@@ -1676,7 +1676,7 @@
                     frame_cnt);
             fclose(stats_file);
 #endif
-            die("Mismatch seen");
+            fatal("Mismatch seen");
           }
         }
       }