RDMA/mlx5: Delete unreachable code

Delete two occurrences of unreachable code discovered by the Coverity.

Link: https://lore.kernel.org/r/20200727095746.495915-1-leon@kernel.org


Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>