[coreboot] New extra-selectors mechanism on superiotool

[Maxim Polyakov]

Hello community!

I am adding support for f81866 and f81966 fintek chips in superiotool:
https://review.coreboot.org/q/topic:%22fintek%22

However, there are some difficulties to make a dump of the registers of
these chips.
Their global LDN0 and HWM registers contain fields that switch the register
banks of these devices. At the same time, these registers contain fields
that should not change after they are configured.

For example, <Port Select Register - Index 27h> register contains:
BANK_PROG_SEL field[3-2] - Bank select for configuration registers (bank
0/1/2/3)
and
PORT_4E_EN[4] - 0: The configuration register port is 2E/2F.
                               1: The configuration register port is 4E/4F.

I suggest introducing a new element in chip configuration for such
registers - an extra selector:
https://review.coreboot.org/c/coreboot/+/83196
It seems to me that this is the optimal solution.

This allows superiotool to configure the register fields to select a bank
before making a correct dump for the corresponding LDN in automatic mode.

Please review.

Thx

// Regards,
// Max