Fix code style, put unused in the end

Change-Id: I7315b35049924d5067203a432584b8f29e5a1391
diff --git a/liblog/logd_write.c b/liblog/logd_write.c
index 6b35a0f..5766f8c 100644
--- a/liblog/logd_write.c
+++ b/liblog/logd_write.c
@@ -80,8 +80,8 @@
     return (g_log_status == kLogAvailable);
 }
 
-static int __write_to_log_null(UNUSED log_id_t log_fd, UNUSED struct iovec *vec,
-        UNUSED size_t nr)
+static int __write_to_log_null(log_id_t log_fd UNUSED, struct iovec *vec UNUSED,
+        size_t nr UNUSED)
 {
     return -1;
 }