net: dsa: mt7530: sync driver-specific behavior of MT7531 variants

net: dsa: mt7530: sync driver-specific behavior of MT7531 variants

MT7531 standalone and MMIO variants found in MT7988 and EN7581 share
most basic properties. Despite that, assisted_learning_on_cpu_port and
mtu_enforcement_ingress were only applied for MT7531 but not for MT7988
or EN7581, causing the expected issues on MMIO devices.

Apply both settings equally also for MT7988 and EN7581 by moving both
assignments form mt7531_setup() to mt7531_setup_common().

This fixes unwanted flooding of packets due to unknown unicast
during DA lookup, as well as issues with heterogenous MTU settings.

Fixes: 7f54cc9772ce ("net: dsa: mt7530: split-off common parts from mt7531_setup")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: Chester A. Unal <chester.a.unal@arinc9.com>
Link: https://patch.msgid.link/89ed7ec6d4fa0395ac53ad2809742bb1ce61ed12.1745290867.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>