hwmon: (lm70) Register hwmon device after creating attribute files, and remove it first

Register hwmon device as last operation in the probe function to ensure that all
attribute files exist when accessed from user applications. Otherwise, there
is a short time frame where the device is registered as hwmon device but
sysfs attributes do not yet exist. This could result in applications erroneously
not detecting attributes.

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