drm/amdgpu: add amdgpu MCA bank dispatch function support

- Refine mca driver code.
- Centralize mca bank dispatch code logic.

Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>