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: NAndrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 5.9.x