drm/amdgpu: drop asd shared memory

asd shared memory is not needed since drivers doesn't
invoke any further cmd to asd directly after the asd
loading. trust application is the one who needs
to talk to asd after the initialization

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>