RDMA/mlx5: Prevent UMR usage with RO only when we have RO caps

RDMA/mlx5: Prevent UMR usage with RO only when we have RO caps

Relaxed ordering is not supported in UMR so we are disabling UMR usage
when user passes relaxed ordering access flag.

Enable using UMR when user requested relaxed ordering but there are no
relaxed ordering capabilities.

This will prevent user from unnecessarily registering a new mkey.

Fixes: 55da1668bd68 ("RDMA/mlx5: Set relaxed ordering when requested")
Link: https://lore.kernel.org/r/20200227113834.94233-1-leon@kernel.org
Signed-off-by: Michael Guralnik <michaelgur@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>