Link against the NFP PMD for vRouter-DPDK

vRouter-DPDK is unable to probe Netronome NICs, since the build system
does not link to the NFP PMD.

Change-Id: Ie022b21e0b2ea05c6b9575f0157a64d568005c46
Partial-Bug: #1774414
Signed-off-by: Frik Botha <frederick.botha@netronome.com>

SConscript

@@ -220,6 +220,7 @@ if sys.platform != 'darwin':
             '-lrte_pmd_i40e',
         #    '-lrte_pmd_fm10k',
             '-lrte_pmd_ixgbe',
+            '-lrte_pmd_nfp',
             '-lrte_pmd_e1000',
         #    '-lrte_pmd_mlx4',
         #    '-lrte_pmd_ring',