hwmon: add driver for Aquacomputer D5 Next

This driver exposes hardware sensors of the Aquacomputer D5 Next
watercooling pump, which communicates through a proprietary USB HID
protocol.

Available sensors are pump and fan speed, power, voltage and current, as
well as coolant temperature. Also available through debugfs are the serial
number, firmware version and power-on count.

Attaching a fan is optional and allows it to be controlled using
temperature curves directly from the pump. If it's not connected,
the fan-related sensors will report zeroes.

The pump can be configured either through software or via its physical
interface. Configuring the pump through this driver is not implemented,
as it seems to require sending it a complete configuration. That
includes addressable RGB LEDs, for which there is no standard sysfs
interface. Thus, that task is better suited for userspace tools.

This driver has been tested on x86_64, both in-kernel and as a module.

Signed-off-by: Aleksa Savic <savicaleksa83@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>