net: Allow NETIF_F_HW_TLS_TX if IP_CSUM && IPV6_CSUM

Cited patch below blocked the TLS TX device offload unless HW_CSUM
is set. This broke devices that use IP_CSUM && IP6_CSUM.
Here we fix it.

Note that the single HW_TLS_TX feature flag indicates support for
both IPv4/6, hence it should still be disabled in case only one of
(IP_CSUM | IPV6_CSUM) is set.

Fixes: ae0b04b2

 ("net: Disable NETIF_F_HW_TLS_TX when HW_CSUM is disabled")
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reported-by: Rohit Maheshwari <rohitm@chelsio.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Link: https://lore.kernel.org/r/20210114151215.7061-1-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>