hwmon: (pmbus/mp2975) Fix PGOOD in READ_STATUS_WORD

MP2973 & MP2971 return PGOOD instead of PB_STATUS_POWER_GOOD_N.
Fix that in the read_word_data hook.

MP2975 should not be affected, but that has not been confirmed with
hardware.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
Link: https://lore.kernel.org/r/20230731092204.2933045-1-Naresh.Solanki@9elements.com


[groeck: Rephrased description to indicate that MP2975 is likely not affected]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>