net/mlx5: fix errno for unsupported Direct Rules

net/mlx5: fix errno for unsupported Direct Rules

When Direct Rules API is not supported we don't set the errno.
This results in failing the function but with errno equals to zero.
The result of this is that a function that failed, is considered as
a function that worked correctly.

This commit fixes this issue by setting the errno to ENOTSUP and
returning this error when error value should be returned.

Since RDMA-CORE are returning positive errno we are also returning
positive error values.

Fixes: 4f84a19779ca ("net/mlx5: add Direct Rules API")

Signed-off-by: Ori Kam <orika@mellanox.com>
Acked-by: Shahaf Shuler <shahafs@mellanox.com>