dpdk: link DPDK with MLX4/MLX5 libraries again

dpdk: link DPDK with MLX4/MLX5 libraries again

 Previously it was linked and worker properly. While rdma build
was simplified, link was lost so all encrypted data won't pass
via Mellanox interfaces(ipsec, ipip, ssh etc) and NetVSC taps
won't created the right way.

 Errors:
mlx5_common: Verbs device not found: 21a5:00:02.0
mlx5_common: Failed to initialize device context.
EAL: Requested device 21a5:00:02.0 cannot be used
 Tested on Azure. Same errors appears on physical machine with
Mellanox connect adapter

Type: fix

Signed-off-by: Vladimir Ratnikov <vratnikov@netgate.com>
Change-Id: Ib68976282e0ed91c016a7318db6b5eddf5510c47