DSA: add a dpdk workload and improve documentation for dpdk use

[tkatila]

Is your feature request related to a problem? Please describe.
Using DSA with DPDK workload requires different configuration. i.e. https://github.com/intel/intel-device-plugins-for-kubernetes/blob/main/demo/dsa.conf#L20 should have a "dpdk_" prefix if it's intended for dpdk.

Describe the solution you'd like
To help with customer adaptation, a demo workload and improved documentation should do.