hwmon: (ltc4151) Convert to devm_hwmon_device_register_with_groups

Use ATTRIBUTE_GROUPS macro and devm_hwmon_device_register_with_groups to
simplify the code a bit.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Tested-by: Per Dalén <per.dalen@appeartv.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>