net/mlx5: Devcom, introduce devcom_for_each_peer_entry

Introduce generic APIs which will retrieve all peers.
This API replace mlx5_devcom_get/release_peer_data which retrieve
only a single peer.

Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>