net/mlx5: fix mask used for IPv6 item validation

net/mlx5: fix mask used for IPv6 item validation

The nic_mask struct in function mlx5_flow_validate_item_ipv6()
includes hop_limits field.
This is redundant since matching on this item is not supported using
Verbs flow engine (dv_flow_en=0).

(Separate patch will be sent to handle this issue for DV flow engine.)

Setting a rule including match on this field will fail:
testpmd> flow create 0 ingress pattern eth / ipv6 hop is 1 / end actions
drop / end
port_flow_complain(): Caught PMD error type 1 (cause unspecified):
hardware refuses to create flow: Operation not supported

This patch removes the redundant field from nic_mask, to ensure that
such flow rules will be rejected by PMD validation:
testpmd> flow create 0 ingress pattern eth / ipv6 hop is 1 / end actions
drop / end
port_flow_complain(): Caught PMD error type 13 (specific pattern item):
cause: 0x7fffffffa2c8, mask enables non supported bits: Operation not
supported

The related lines in function flow_verbs_translate_item_ipv6() are
removed as well, since they are redundant.

Fixes: 23c1d42c7138 ("net/mlx5: split flow validation to dedicated function")
Fixes: 84c406e74524 ("net/mlx5: add flow translate function")
Cc: stable@dpdk.org
Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>