hwmon: add OneXPlayer mini AMD sensors driver

hwmon: add OneXPlayer mini AMD sensors driver

Sensors driver for OXP Handhelds from One-Netbook that expose fan reading
and control via hwmon sysfs.

As far as I could gather all OXP boards have the same DMI strings and
they can be told appart only by the boot cpu vendor (Intel/AMD).
Currently only AMD boards are supported since Intel have different EC
registers and values to read/write.

Fan control is provided via pwm interface in the range [0-255]. AMD
boards have [0-100] as range in the EC, the written value is scaled to
accommodate for that.

Signed-off-by: Joaquín Ignacio Aramendía <samsagax@gmail.com>
Link: https://lore.kernel.org/r/20221104140659.593608-1-samsagax@gmail.com
[groeck: Removed misleading comment about module_platform_driver()]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>