rdma/cxgb4: Prevent potential integer overflow on 32bit

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.

Fixes: 1cab775c3e75 ("RDMA/cxgb4: Fix LE hash collision bug for passive open connection")
Link: https://patch.msgid.link/r/86b404e1-4a75-4a35-a34e-e3054fa554c7@stanley.mountain
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>