hwmon: (core) fix resource leak on devm_kcalloc failure

If dev_kcalloc fails to allocate hw_dev->groups then the current
exit path is a direct return, causing a leak of resources such
as hwdev and ida is not removed.  Fix this by exiting via the
free_hwmon exit path that performs the necessary resource cleanup.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>