hwmon: (gpd-fan) Fix range check for pwm input

hwmon: (gpd-fan) Fix range check for pwm input

Fixed the maximum value in the PWM input range check, allowing the
input to be set to 255.

Fixes: 0ab88e239439 ("hwmon: add GPD devices sensor driver")
Reported-by: Chenx Dust <chenx_dust@outlook.com>
Link: https://github.com/Cryolitia/gpd-fan-driver/pull/18
Co-developed-by: Chenx Dust <chenx_dust@outlook.com>
Signed-off-by: Chenx Dust <chenx_dust@outlook.com>
Signed-off-by: Cryolitia PukNgae <cryolitia@uniontech.com>
Link: https://lore.kernel.org/r/20250919-hwmon-v1-1-2b69c8b9c062@uniontech.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>