vdpa: Enable strict validation for netlinks ops

The previous patches added the missing nla policies that were required for
validation to work.

Now strict validation on netlink ops can be enabled. This patch does it.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Cc: stable@vger.kernel.org
Message-Id: <20230727175757.73988-9-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>