dsa: updated api to use net_if

Change DSA API to use `net_if` directly to make API calls instead of
indirectly via `dsa_context` and `switch_id`.
Remove unused `switch_id`, `switch_enable_port`, and `dsa_get_context`.

Signed-off-by: Arvin Farahmand <arvinf@ip-logix.com>
3 files changed