drm/amdgpu: add new DF callback for ECC setup

The ForceParWrRMW setting needs to be enabled for ECC, but disabled
when ECC is not enabled.

Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>