net: ethernet: mediatek: split tx and rx fields in mtk_soc_data struct

Split tx and rx fields in mtk_soc_data struct. This is a preliminary
patch to roll back to ADMAv1 for MT7986 and MT7981 SoC in order to fix a
hw hang if the device receives a corrupted packet when using ADMAv2.0.

Fixes: 197c9e9 ("net: ethernet: mtk_eth_soc: introduce support for mt7986 chipset")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://lore.kernel.org/r/70a799b1f060ec2f57883e88ccb420ac0fb0abb5.1715164770.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>