port: fix pcap source parameter check
port: fix pcap source parameter check

This patch fixes source port parameter checking logic.
Originally, if user set field "file_name" with meaning value
but leave PCAP support feature disabled, the program simply
ignores this field without notifying the user.

Fixes: d4b42133d85b ("port: add pcap file source")

Signed-off-by: Fan Zhang <b46d470dc79aa6fd718cd24d07380f6203b7fc3c@intel.com>
Acked-by: Cristian Dumitrescu <25468b8a3698eeb3c368247f8635924bb4a1ce2c@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk