hwmon: (f71805f) Fix clamping of temperature limits

Properly clamp temperature limits set by the user. Without this fix,
attempts to write temperature limits above the maximum supported by
the chip (255 degrees Celsius) would arbitrarily and unexpectedly
result in the limit being set to 0 degree Celsius.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>