MAINTAINERS: Add myself as mlx5_vdpa driver

As Eli Cohen moved to other work, I'll be the contact point for
mlx5_vdpa.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Message-Id: <20230925160654.1558627-1-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>