hwmon: Add KEBA fan controller support

The KEBA fan controller is found in the system FPGA of KEBA PLC devices.
It detects if the fan is removed or blocked. For fans with tacho signal
the monitoring of the speed of the fan is supported. It also supports to
regulate the speed of fans with PWM input.

The auxiliary device for this driver is instantiated by the cp500 misc
driver.

Signed-off-by: Gerhard Engleder <eg@keba.com>
Link: https://lore.kernel.org/r/20250425194823.54664-1-gerhard@engleder-embedded.com


[groeck: Added various missing "break;" statements]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>