drm/amdgpu: don't attach the tlb fence for SI

drm/amdgpu: don't attach the tlb fence for SI

SI hardware doesn't support pasids, user mode queues, or
KIQ/MES so there is no need for this.  Doing so results in
a segfault as these callbacks are non-existent for SI.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4744
Fixes: f3854e04b708 ("drm/amdgpu: attach tlb fence to the PTs update")
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>