hwmon: (sch5627) Add support for writing limit registers

hwmon: (sch5627) Add support for writing limit registers

After some testing on a Fujitsu Esprimo P720, it turned out that
the limit registers are indeed writable and affect the fan control
algorithm. This is supported by the datasheet, which says that the
fan control functions are based on the limit and parameter registers.
Since accessing those registers is very inefficient, the existing
regmap cache is used to cache those registers values.

Tested on a Fujitsu Esprimo P720.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20230907052639.16491-5-W_Armin@gmx.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>