hwmon: (lm85) Let the user set the fan min limit to 0

Trying to set the fan min limit to 0 currently writes 0 to the
register, which is an invalid value. It's read back as -1 and the
alarm flag is raised. Instead we should write 0xffff (maximum
value), which reads back as 0 and no alarm flag is raised.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Juerg Haefliger <juergh at gmail.com>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>