net: enetc: add LSO support for i.MX95 ENETC PF

ENETC rev 4.1 supports large send offload (LSO), segmenting large TCP
and UDP transmit units into multiple Ethernet frames. To support LSO,
software needs to fill some auxiliary information in Tx BD, such as LSO
header length, frame length, LSO maximum segment size, etc.

At 1Gbps link rate, TCP segmentation was tested using iperf3, and the
CPU performance before and after applying the patch was compared through
the top command. It can be seen that LSO saves a significant amount of
CPU cycles compared to software TSO.

Before applying the patch:
%Cpu(s):  0.1 us,  4.1 sy,  0.0 ni, 85.7 id,  0.0 wa,  0.5 hi,  9.7 si

After applying the patch:
%Cpu(s):  0.1 us,  2.3 sy,  0.0 ni, 94.5 id,  0.0 wa,  0.4 hi,  2.6 si

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://patch.msgid.link/20241219054755.1615626-4-wei.fang@nxp.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>