drm/amdgpu: initialize ras structures for xgmi block (v2)

init ras common interface and fs node for xgmi block

v2: remove unnecessary physical node number check before
invoking amdgpu_xgmi_ras_late_init

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>