net: ethernet: mtk_wed: debugfs: move wed_v2 specific regs out of regs array

Move specific WED2.0 debugfs entries out of regs array. This is a
preliminary patch to introduce WED 3.0 debugfs info.

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