RDMA/cm: Remove unused store to ret in cm_rej_handler

The 'goto out' label doesn't read ret, so don't set it.

Link: https://lore.kernel.org/r/20200506074701.9775-4-leon@kernel.org
Signed-off-by: Danit Goldberg <danitg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>