hwmon: (abx500) Switch to using the new API kobj_to_dev()

fixed the following coccicheck:
drivers/hwmon/abx500.c:266:60-61: WARNING opportunity for kobj_to_dev().

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Link: https://lore.kernel.org/r/1606357280-51921-1-git-send-email-tiantao6@hisilicon.com


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