netdev-dpdk: linear buffer check with zero-copy

netdev-dpdk: linear buffer check with zero-copy

As of DPDK 19.11, in order to use dequeue-zero-copy in DPDK Vhost library,
the application has to disable the linear buffer option. Hence
dequeue-zero-copy is not supported for vhost application that requires
linear buffers.

An alternative DPDK based approach to disable the linear buffers within
the vhost library itself was proposed in [1], however the consensus was
that application should be responsible for disabling linear buffers.

As such this patch disables linear buffers when zero-copy is enabled.

[1]    https://patches.dpdk.org/patch/67200/

Fixes: 127b6a6eea02 ("dpdk: Update to use DPDK 19.11.")
Signed-off-by: Sivaprasad Tummala <Sivaprasad.Tummala@intel.com>
Acked-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>