net: ethernet: mediatek: add more resets for internal ethernet circuit block

struct mtk_eth has already contained struct regmap ethsys pointer
to the address range of the internal circuit reset, so we reuse it
to reset more internal blocks on ethernet hardware such as packet
processing engine (PPE) and frame engine (FE) instead of rstc which
deals with FE only.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>