test: Fix test-dpif-dpdk unit tests

- Add alloc/free queues to dpdk-ring-stub.c
- Make test-dpdk-link.c use dpdk-ring-stub.c removing a duplicated
  function.

Change-Id: I22cab8c2eba8a6f3e1cf33e78075864c9875b9a3
Reviewed-by: Mark D. Gray <mark.d.gray@intel.com>
Reviewed-by: Eimear Morrissey <eimear.morrissey@intel.com>
Reviewed-by: Stephen Finucane <stephen.finucane@intel.com>
Signed-off-by: Nicolas Pernas Maradei <nicolasx.pernas.maradei@intel.com>
datapath/Makefile: add dependencies between targets

Add missing dependencies between vport and vport_ut targets preventing
building issues due to tasks executed out of sync.

Change-Id: I0f47972f8363e5f02f1122a702f5c0591150bb80
Reviewd-by: Mark D. Gray <mark.d.gray@intel.com>
Signed-off-by: Nicolas Pernas Maradei <nicolasx.pernas.maradei@intel.com>
NEWS.md: update

Added userspace vhost device type to NEWS.md

Change-Id: Id7e3a0a5dcfe011a5a8844cc1738664ad7c7e384
Reviewed-by: Mark D. Gray <mark.d.gray@intel.com>
Signed-off-by: Anthony Fee <anthonyx.fee@intel.com>