drm/amd/pm: Disable fan control if not supported

On arcturus, not all platforms use PMFW based fan control. On such
ASICs fan control by PMFW will be disabled in PPTable. Disable hwmon
knobs for fan control also as it is not possible to report or control
fan speed on such platforms through driver.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>