IB/mlx5: Fix some spelling mistakes

Fix spelling mistakes in remarks
    "retrun"->"return"
    "Decalring"->"Declaring"

Signed-off-by: Talat Batheesh <talatb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>