drm/amdgpu/soc21: don't remap HDP registers for SR-IOV

This matches the behavior for soc15 and nv.

Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Timmy Tsai <timmtsai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>