test: l2fwd: re-organize functions
test: l2fwd: re-organize functions

Re-order functions to get rid off (static) function prototypes
and improve code readability.

Signed-off-by: Petri Savolainen <d528fd253b9aaf78fa72edbcc6249e82047f6ce6@nokia.com>
Reviewed-and-tested-by: Stuart Haslam <1fce01f364ef5298e64e07a42e08efeef153fa98@linaro.org>
Signed-off-by: Maxim Uvarov <db4d16e02ae2d7493db430203537da8b2e34f290@linaro.org>

ravineet-singh/odp,ravineet-singh/odp,erachmi/odp,dkrot/odp,erachmi/odp,erachmi/odp,ravineet-singh/odp,mike-holmes-linaro/odp,mike-holmes-linaro/odp,dkrot/odp,rsalveti/odp,nmorey/odp,mike-holmes-linaro/odp,nmorey/odp,ravineet-singh/odp,dkrot/odp,rsalveti/odp,rsalveti/odp,nmorey/odp,rsalveti/odp,mike-holmes-linaro/odp,erachmi/odp,nmorey/odp,dkrot/odp,rsalveti/odp