RDMA/mlx5: Verify that DM operation is reasonable

Fix the complaint from smatch by verifing that the user requested DM
operation is not greater than 31.

divers/infiniband/hw/mlx5/dm.c:220 mlx5_ib_handler_MLX5_IB_METHOD_DM_MAP_OP_ADDR()
error: undefined (user controlled) shift '(((1))) << op'

Fixes: cea85fa5 ("RDMA/mlx5: Add support in MEMIC operations")
Link: https://lore.kernel.org/r/458b1d7710c3cf01360c8771893f483665569786.1620711734.git.leonro@nvidia.com


Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>