drm/amdgpu: add helper funcs to detect PCS error

Since from vega20, hardware supports run-time detect
and report XGMI/WAFL PCS ras error. Add helper functions
to walkthrough every type of ras error and report it if
any.

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>