Add extern "C" in rte_pmd_i40e.h when be compiled with CPP. Fixes: 17e906a1ea9c ("net/i40e: support link status notification") Cc: stable@dpdk.org Signed-off-by: Prateek Agarwal <prateekag@cse.iitb.ac.in> Acked-by: Qi Zhang <qi.z.zhang@intel.com>