Log an error message if opening a device fails

utils/nfc-probe.c

@@ -115,7 +115,9 @@ main (int argc, const char *argv[])
         }
       }
       nfc_close (pnd);
-    }
+    } else {
+		printf("nfc_open failed for %s\n", connstrings[i]);
+	}
   }
   res = EXIT_SUCCESS;