hwmon: (max1619) Fix critical alarm display

The overtemperature status bit, which is used to display critical alarm status,
matches the output of the OVERT signal 1:1. If that signal is active-low, the
bit will read 1 if there is no alarm. It is therefore necessary to reverse
the bit in this case.

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