drm/amdgpu: clean up asd on the ta_firmware_header_v2_0

On the psp13 series use ta_firmware_header_v2_0 and the asd firmware
was buildin ta, so needn't request asd firmware separately.

Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Yifan Zhang <yifan1.zhang@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>