hwmon: Add Congatec Board Controller monitoring driver

hwmon: Add Congatec Board Controller monitoring driver

Add support for the Congatec Board Controller. This controller exposes
temperature, voltage, current and fan sensors.

The available sensors list cannot be predicted. Some sensors can be
present or not, depending the system.
The driver has an internal list of all possible sensors, for all Congatec
boards. The Board Controller gives to the driver its sensors list, and
their status (active or not).

Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
Link: https://lore.kernel.org/r/20250203-congatec-board-controller-hwmon-v4-1-ff6c76a4662c@bootlin.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>