hwmon: (pmbus) Introduce page_change_delay

We have some buggy pmbus devices that require a delay after performing a
page change operation before trying to issue more commands to the
device.

This allows for a configurable delay after page changes, but not
affecting other read or write operations.

This makes a slight behavioral tweak to the existing delay logic, where
it considers the longest of delays between operations, instead of always
chosing the write delay over the access delay.

Signed-off-by: William A. Kennington III <william@wkennington.com>
Link: https://lore.kernel.org/r/20250407201002.1198092-1-william@wkennington.com


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