net/mlx5e: Have a single RSS Toeplitz hash key

No need to generate a unique key per TIR.
Generating a single key per netdev and copying it to all
its TIRs.

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