net: dsa: mv88e6xxx: Add support for model-specific pre- and post-reset handlers

Instead of calling mv88e6xxx_g2_eeprom_wait() directly from
mv88e6xxx_hardware_reset(), add configurable pre- and post-reset hard
reset handlers. Initially, the handlers are set to
mv88e6xxx_g2_eeprom_wait() for all families that have get/set_eeprom()
to match the existing behavior. No functional change intended (except
for additional error messages on failure).

Fixes: 6ccf50d4 ("net: dsa: mv88e6xxx: Avoid EEPROM timeout when EEPROM is absent")
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>