hwmon: (pmbus/bpa-rs600) Add workaround for incorrect Pin max

BPD-RS600 modules running firmware v5.70 misreport the MFR_PIN_MAX.
The indicate a maximum of 1640W instead of 700W. Detect the invalid
reading and return a sensible value instead.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20210812014000.26293-3-chris.packham@alliedtelesis.co.nz


Signed-off-by: Guenter Roeck <linux@roeck-us.net>