hwmon: (axi-fan-control) Make sure the clock is enabled

The core will only work if it's clock is enabled. This patch is a
minor enhancement to make sure that's the case.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210811114853.159298-2-nuno.sa@analog.com


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