drm/amdgpu: Actually check flags for all context ops.

Missing validation ...

Checked libdrm and it clears all the structs, so we should be
safe to just check everything.

Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit c6b86421)
Cc: stable@vger.kernel.org