[dts] [PATCH V1] tests/checksum_offload: rework l4 tx/rx test case

[Tu, Lijuan]

> 1. Fix incorrect payload of SCTP package.
> 2. Fix vxlan package errors.
> 3. Improve contracting efficiency and add debugging information.
> 
> Signed-off-by: ChenBo <box.c.chen at intel.com>

Applied