net/mlx5e: Set netdev->rx_cpu_rmap on netdev creation

To simplify mlx5e_open_locked flow we set netdev->rx_cpu_rmap on netdev
creation rather on netdev open, it is redundant to set it every time on
mlx5e_open_locked.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>