net: ethernet: mtk_eth_soc: enable nft hw flowtable_offload for MT7988 SoC

Enable hw Packet Process Engine (PPE) for MT7988 SoC.

Tested-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/5e86341b0220a49620dadc02d77970de5ded9efc.1690441576.git.lorenzo@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>