dell-smm-hwmon.c: Add XPS 9570 to supported devices list

Allow the module to be loaded on Dell XPS 9570, without having to
provide the "force=1" option.

Signed-off-by: Michele Sorcinelli <michelesr@autistici.org>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>