tests/amdgpu: expand write linear helper for security (v3)

This patch expand write linear helper for security to submit the command
with secure context.

v2: refine the function implementation.
v3: remove amdgpu_cs_ctx_create3.

Acked-by: Huang Rui <ray.huang@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Aaron Liu <aaron.liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>