net/virtio: fix memory init with vDPA backend

net/virtio: fix memory init with vDPA backend

This patch fixes an overhead met with mlx5-vdpa Kernel
driver, where for every page in the mapped area, all the
memory tables gets updated. For example, with 2MB hugepages,
a single IOTLB_UPDATE for a 1GB region causes 512 memory
updates on mlx5-vdpa side.

Using batching mode, the mlx5 driver will only trigger a
single memory update for all the IOTLB updates that happen
between the batch begin and batch end commands.

Fixes: 6b901437056e ("net/virtio: introduce vhost-vDPA backend")
Cc: stable@dpdk.org
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>