drm/amdgpu: job is secure iff CS is secure (v5)

Mark a job as secure, if and only if the command
submission flag has the secure flag set.

v2: fix the null job pointer while in vmid 0
submission.
v3: Context --> Command submission.
v4: filling cs parser with cs->in.flags
v5: move the job secure flag setting out of amdgpu_cs_submit()

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>