net: ethernet: mtk_wed: debugfs: add WED 3.0 debugfs entries

Introduce WED3.0 debugfs entries useful for debugging.

Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Sujuan Chen <sujuan.chen@mediatek.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>