drm/amd/powerplay: wrong control mode cause the fan spins faster unnecessarily

The fan control mode can either be FDO_PWM_MODE_STATIC or FDO_PWM_MODE_STATIC_RPM.
Setting it as AMD_FAN_CTRL_AUTO will cause the fan spin faster wrongly.

This can be reproduced by:
'# cat /sys/class/hwmon/hwmon0/pwm1
   38
'# cat /sys/class/hwmon/hwmon0/pwm1_enable
   2
'# echo "2" > /sys/class/hwmon/hwmon0/pwm1_enable
'# cat /sys/class/hwmon/hwmon0/pwm1
   122
The fan speed get faster wrongly even with its original mode echo back.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org