rdma/cxgb4: Prevent potential integer overflow on 32bit

In the Linux kernel, the following vulnerability has been resolved: rdma/cxgb4: Prevent potential integer overflow on 32bit The "gl->tot_len" variable is controlled by the user. It comes from process_responses(). On 32bit systems, the "gl->tot_len + sizeof(struct cpl_pass_accept_req) + sizeof(struct rss_header)" addition could have an integer wrapping bug. Use size_add() to prevent this.