bnxt_en: add support for tcp-data-split ethtool command

bnxt_en: add support for tcp-data-split ethtool command

NICs that uses bnxt_en driver supports tcp-data-split feature by the
name of HDS(header-data-split).
But there is no implementation for the HDS to enable by ethtool.
Only getting the current HDS status is implemented and The HDS is just
automatically enabled only when either LRO, HW-GRO, or JUMBO is enabled.
The hds_threshold follows rx-copybreak value. and it was unchangeable.

This implements `ethtool -G <interface name> tcp-data-split <value>`
command option.
The value can be <on> and <auto>.
The value is <auto> and one of LRO/GRO/JUMBO is enabled, HDS is
automatically enabled and all LRO/GRO/JUMBO are disabled, HDS is
automatically disabled.

HDS feature relies on the aggregation ring.
So, if HDS is enabled, the bnxt_en driver initializes the aggregation ring.
This is the reason why BNXT_FLAG_AGG_RINGS contains HDS condition.

Acked-by: Jakub Kicinski <kuba@kernel.org>
Tested-by: Stanislav Fomichev <sdf@fomichev.me>
Tested-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20250114142852.3364986-8-ap420073@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>