drm/amdgpu: Validate VM ioctl flags.

drm/amdgpu: Validate VM ioctl flags.

BugLink: https://bugs.launchpad.net/bugs/2033931
commit a2b308044dcaca8d3e580959a4f867a1d5c37fac upstream.

None have been defined yet, so reject anybody setting any. Mesa sets
it to 0 anyway.

Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>