drm/amdgpu: Modify the compilation failed problem when other ras blocks' .h include amdgpu_ras.h

Modify the compilation failed problem when other ras blocks' .h include amdgpu_ras.h.

v2: squash in forward declaration warning fix (Alex)

Signed-off-by: yipechai <YiPeng.Chai@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: John Clements <john.clements@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>