Re: [RFC PATCH 1/1] mv88e6xxx: Cache scratch config of 6352 in setup

In mv88e6352 scratch register in Global Control 2 set of registers
returns which port is attached to SERDES. This value is set and
stays constant after the switch is released from reset; thus, it
can be cached during chip setup instead of reading the register
everytime when SERDES config is needed.

1. Add setup_chip_specific member to mv88e6xxx_ops and
g2_scratch_config3 member to mv88e6xxx_chip.
2. Add mv88e6352_g2_cache_global_scratch_config3 function as
.setup_chip_specific which reads the CONFIG3 value from the scratch
register and caches it.
3. Call .setup_chip_specific during chip setup.

Can we actually use setup_errata for this instead of adding a new member
to mv88e6xxx_ops?

Thank you for your reviews in advance.

Best,
Fidan