net/mlx5: DR, handle more than one peer domain

Currently, DR domain is using the assumption that each domain can only
have a single peer.
In order to support VF LAG of more then two ports, expand peer domain
to use an array of peers, and align the code accordingly.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>