[qca-nss-ecm] Add DSCP classifier

Remove existing DSCP mark code from front end files.
Add DSCP mark code as a classifier in its own right.

Change-Id: Ifc9375aa9025bebdc122c33ded8267d2e8b035b9
Signed-off-by: Gareth Williams <garethw@codeaurora.org>
8 files changed