drm/amdgpu: Add C2PMSG_109/126 reg field shift/masks

Add MP0_C2PMSG_109/126 register field shift/masks
that are used to identify boot status by driver.

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