example: l3fwd: optimize ip checksum update
example: l3fwd: optimize ip checksum update

When decrementing TTL the IPv4 checksum can be incrementally updated.

Signed-off-by: Matias Elo <62402263e8617147f0e4dd5b7f6f8ec67f2b3d2c@nokia.com>
Reviewed-by: Mike Holmes <ed44c09f4d7f698f5510adc894a872c73e08c8bd@linaro.org>
Signed-off-by: Maxim Uvarov <db4d16e02ae2d7493db430203537da8b2e34f290@linaro.org>

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