net/mlx5e: Remove the mlx5e_update_priv_params() function

It was used to update netdev priv parameters that require stopping
and re-opening the device in a generic way - it got the new
parameters and did: ndo_stop(), copy new parameters into current
parameters, ndo_open().

We chose to remove it for two reasons:
1) It requires additional instance of struct mlx5e_params on the
   stack and looking forward we expect this struct to grow.
2) Sometimes we want to do additional operations (besides
   just updating the priv parameters) while the netdev is stopped.
   For example, updating netdev->mtu @mlx5e_change_mtu() should
   be done while the netdev is stopped (done in this commit).

Signed-off-by: Achiad Shochat <achiad@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>