examples/skeleton: fix NUMA check of port and core

examples/skeleton: fix NUMA check of port and core

According to the comments and logging, the author just hope user to use
the core and device which are in the same numa node for optimal
performance. If not, A warning gives out.

This patch fixes the check for a device on the node 0.

Fixes: 7107e471a6c7 ("examples/skeleton: very simple code for packet forwarding")
Cc: stable@dpdk.org
Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>