net: libwx: fix Tx L4 checksum
In the Linux kernel, the following vulnerability has been resolved:

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.