net/mlx5: E-Switch, Add eswitch pointer to each representor

Store the managing E-Switch of each representor. This will be used
when a representor is created on eswitch manager 0 but the vport
belongs to eswitch manager 1.

Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>