net: libwx: fix Tx L4 checksum

The hardware only supports L4 checksum offload for TCP/UDP/SCTP protocol.
There was a bug to set Tx checksum flag for the other protocol that results
in Tx ring hang. Fix to compute software checksum for these packets.

Fixes: 3403960c ("net: wangxun: libwx add tx offload functions")
Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Link: https://patch.msgid.link/20250324103235.823096-2-jiawenwu@trustnetic.com


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