drm/amdgpu/gfx9: switch to golden tsc registers for renoir+

Renoir and newer gfx9 APUs have new TSC register that is
not part of the gfxoff tile, so it can be read without
needing to disable gfx off.

Acked-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>