drm/amdgpu: init gds config for arct

arct has 4KB gds (4 banks inside) so the max_wave_id
should be 0xfff

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Le Ma <Le.Ma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>