net/dpdk-20.11: update to point release 20.11.8

Update dpdk-20.11 port to the latest point release version.
This update also includes cleanup for the makefile, as suggested
by portclippy & portfmt.

Changelog: http://inbox.dpdk.org/announce/20220829150456.2223782-1-xuemingl@nvidia.com
Changelog: http://inbox.dpdk.org/announce/20221213140809.3845954-1-luca.boccassi@gmail.com
Changelog: http://inbox.dpdk.org/announce/20230427184829.1368323-1-luca.boccassi@gmail.com

PR: 271225