drm/amdgpu: set TMZ bits in PTEs for secure BO (v4)

If a buffer object is secure, i.e. created with
AMDGPU_GEM_CREATE_ENCRYPTED, then the TMZ bit of
the PTEs that belong the buffer object should be
set.

v1: design and draft the skeletion of TMZ bits setting on PTEs (Alex)
v2: return failure once create secure BO on non-TMZ platform  (Ray)
v3: amdgpu_bo_encrypted() only checks the BO (Luben)
v4: move TMZ flag setting into amdgpu_vm_bo_update  (Christian)

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
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>