net: ethernet: mtk_eth_soc: rely on MTK_MAX_DEVS and remove MTK_MAC_COUNT

Get rid of MTK_MAC_COUNT since it is a duplicated of MTK_MAX_DEVS.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/1856f4266f2fc80677807b1bad867659e7b00c65.1690246066.git.daniel@makrotopia.org


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