hwmon: (pmbus/core) Treat parameters as paged if on multiple pages

Some chips have attributes which exist on more than one page but the
attribute is not presently marked as paged. This causes the attributes
to be generated with the same label, which makes it impossible for
userspace to tell them apart.

Marking all such attributes as paged would result in the page suffix
being added regardless of whether they were present on more than one
page or not, which might break existing setups. Therefore, we add a
second check which treats the attribute as paged, even if not marked as
such, if it is present on multiple pages.

Fixes: b4ce237b ("hwmon: (pmbus) Introduce infrastructure to detect sensors and limit registers")
Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>