drm/amdgpu: enable error injection to XGMI block via debugfs

allow inject error to XGMI block via debugfs node ras_ctrl

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>