Add ib preemption status in amdgpu_job, so that ring level function
can detect preemption and program for resuming it.

v2: squash in fix to restore job->preamble_status back to status value (Jack)
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Jack Xiao <Jack.Xiao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>