net/mlx5e: IPoIB, Initialize max_opened_tc in mlx5i_init flow

Enhanced ipoib does not initialize max_opened_tc causing wrong ethtool
statistics. As mlx5e_grp_sw_update_stats relies on this variable, without
this change, the TX statistics will not be updated.

Fixes: 05909bab ("net/mlx5e: Avoid reset netdev stats on configuration changes")
Signed-off-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>