[dts] l3fwd tests

[David Marchand]

Hello,

- Looking at l3fwd tests in dts, I noticed it still relies on
USER_FLAGS= black magic which was dropped with makefile support
removal.
See fda34680eb9a ("examples: remove legacy sections of makefiles").

This requires a fix if the intention is still to test the different
lookup methods.


- A change has been proposed on l3fwd, that will change the expected
network traffic.
https://patchwork.dpdk.org/project/dpdk/list/?series=20336
Especially:
https://patchwork.dpdk.org/project/dpdk/patch/20211105083851.2812-3-pbhagavatula@marvell.com/

Please confirm DTS will be fine with this change.


-- 
David Marchand