app/testpmd: display devargs in port info output

app/testpmd: display devargs in port info output

Devargs may affect how device works but currently we don't have a
way to observe provided devargs.

Add ability to print device argument as part of port info,

For example, for "--vdev net_pcap0,iface=lo" output will be

"
********************* Infos for port 1  *********************
MAC address: 02:70:63:61:70:00
Device name: net_pcap0
Driver name: net_pcap
Devargs: iface=lo
....
"

or for "-w0000:86:00.1,queue-num-per-vf=8",

"
********************* Infos for port 0  *********************
MAC address: 3C:FD:FE:AB:B4:41
Device name: 0000:86:00.1
Driver name: net_i40e
Devargs: queue-num-per-vf=8
....
"

`Devargs` line may not be printed at all if devargs is not provided for
that device.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Bernard Iremonger <bernard.iremonger@intel.com>