drm/amdgpu: Avoid hive seqno increment in legacy ras

drm/amdgpu: Avoid hive seqno increment in legacy ras

The hive->event_mgr variable is used by both ras module
and legacy ras. To ensure the continuity of hive seqno
growth, after enabling ras module, it is forbidden to
operate the event_mgr variable in legacy ras.

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