psp sysfs not cleaned up on driver unload for sienna_cichlid

Fixes: ce87c98d ("drm/amdgpu: Include sienna_cichlid in USBC PD FW support.")
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>