net/mlx5e: Compare all fields in IPv6 address

Fix size argument in memcmp to compare whole IPv6 address.

Fixes: b3beba1f ("net/mlx5e: Allow policies with reqid 0, to support IKE policy holes")
Reviewed-by: Raed Salem <raeds@nvidia.com>
Reviewed-by: Emeel Hakim <ehakim@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>