hwmon: (raspberrypi) Use generic notification mechanism

Use hwmon_notify_event() to make the code easier to
understand and to also generate udev events.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20210905190049.11381-1-W_Armin@gmx.de


Signed-off-by: Guenter Roeck <linux@roeck-us.net>