Add logging for recieved serial bytes on the jevois

Change-Id: I5122a14e2e44d1048c6896e5779e20c2ea7d7f93
diff --git a/y2019/vision/target_sender.cc b/y2019/vision/target_sender.cc
index 06235ff..f322aeb 100644
--- a/y2019/vision/target_sender.cc
+++ b/y2019/vision/target_sender.cc
@@ -382,6 +382,7 @@
       char data[kBufferSize];
       ssize_t n = read(itsDev, &data[0], kBufferSize);
       if (n >= 1) {
+        LOG(INFO, "Serial bytes: %zd", n);
         cobs.ParseData(gsl::span<const char>(&data[0], n));
         auto packet = cobs.received_packet();
         if (!packet.empty()) {