drm/amdgpu: add UAPI to create secure commands (v3)

Add a flag to the command submission IOCTL
structure which when present indicates that this
command submission should be treated as
secure. The kernel driver uses this flag to
determine whether the engine should be
transitioned to secure or unsecure, or the work
can be submitted to a secure queue depending on
the IP.

v3: the flag is now at command submission IOCTL

Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>