Allocating the sysfs attribute name only if needed and only with the
required minimum length looks optimal, but does not take the additional
overhead for both devm_ data structures and the allocation header itself
into account. This also results in unnecessary memory fragmentation.
Move the sysfs name string into struct hwmon_device_attribute and give it
a sufficient length to reduce this overhead.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>