hwmon: (mlxreg-fan) Extend number of supported fans

Some new big modular systems can be equipped with up to 24 fans.
Extend maximum number of fans accordingly.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20230824164006.26868-1-vadimp@nvidia.com


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