hwmon: (lm63) Add basic support for LM64

The LM64 appears to be an LM63 with added GPIO lines. Add support for the
hwmon functionality - GPIO can be added at some later stage if someone
has a need for them.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>