hwmon: (axi-fan-control) Use hwmon_notify_event

Instead of directly accessing kobj directly from the driver, use the
hwmon notify API.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220308135408.440744-1-nuno.sa@analog.com


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