app/testpmd: add device related commands

app/testpmd: add device related commands

With the latest published interface of
rte_eal_hotplug_[add,remove](), and rte_eth_dev_close(),
rte_eth_dev_close() would cleanup all the data structures of
port's eth dev leaving the device common resource intact
if RTE_ETH_DEV_CLOSE_REMOVE is set in dev flags.

So a new command "detach device" (~hotplug remove) to work,
with device identifier like "port attach" is added
to be able to detach closed devices.

Also to display currently probed devices, another command
"show device info <identifier>|all" is also added as a
part of this change.

Signed-off-by: Nithin Dabilpuram <ndabilpuram@marvell.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>