hwmon: (mlxreg-fan) Extend the maximum number of tachometers

Extend support of maximum tachometers from 12 to 14 in order to support
new systems, equipped with more fans.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20210916194719.871413-2-vadimp@nvidia.com


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