drm/amdgpu: add graphic pipeline implementation for si v8

v5: rebase fixes
v6: rebase fixes
v7: rebase fixes
    fix tile reg offset as noticed by Jonathan
    Drop some debugging remnants
v8: add gfx v6 firmware versions for sysfs dump

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Ken Wang <Qingqing.Wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>