app/testpmd: display port driver name

app/testpmd: display port driver name

This makes it easier to check which driver name is reported through ethdev
rte_eth_dev_info_get().

Example:

./build/app/testpmd -c 0x6 --vdev net_af_packet0,iface=mgmt0 --
	-i  --total-num-mbufs 2049
[snip]
testpmd> show port info all

********************* Infos for port 0  *********************
MAC address: DE:AD:DE:01:02:03
Driver name: net_af_packet
Connect to socket: 0
memory allocation on the socket: 0

Signed-off-by: David Marchand <david.marchand@6wind.com>
Acked-by: John McNamara <john.mcnamara@intel.com>