drm/amdgpu: Fix HDP flush for VFs on nbio v7.9

HDP flush remapping is not done for VFs. Keep the original offsets in VF
environment.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>