net: ethernet: mtk_wed: introduce versioning utility routines

Similar to mtk_eth_soc, introduce the following wed versioning
utility routines:
- mtk_wed_is_v1
- mtk_wed_is_v2

This is a preliminary patch to introduce WED support for MT7988 SoC

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>